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  • Precisely position a chart in Excel

    - by ldigas
    When making a chart in the worksheet (not an independent sheet), is there a way to positon it a little more precise ? Instead of just leaving it there "floating" ? I'm having a bunch of tables, one under another, and every table is gonna have to have its own chart. Is there a way when I copy the first one, under the second one (just change the data) to make them exactly one under another ... not "wiggling" left/right ?

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  • Sum if ONLY all the cells have a value?

    - by Mike
    Hi I need to sum 9 cells of data, each one on a separate sheet, but always in the same location. I only want a figure returned when all the cells have data, even if it's a 0. But, if one of the cells is blank I want a blank return. I'm trying to get my head around, making it up actually, where the IFs and ISBLANK and SUMS would go. Any pointers would be greatly appreciated. SUM(IF(ISBLANK(RANGEA,OR(RANGEB),0,ALLRANGES))) Many thanks Michael

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  • export data from WCF Service to excel

    - by Dave
    I need to provide an export to excel feature for a large amount of data returned from a WCF web service. The code to load the datalist is as below: List<resultSet> r = myObject.ReturnResultSet(myWebRequestUrl); //call to WCF service myDataList.DataSource = r; myDataList.DataBind(); I am using the Reponse object to do the job: Response.Clear(); Response.Buffer = true; Response.ContentType = "application/vnd.ms-excel"; Response.AddHeader("Content-Disposition", "attachment; filename=MyExcel.xls"); StringBuilder sb = new StringBuilder(); StringWriter sw = new StringWriter(sb); HtmlTextWriter tw = new HtmlTextWriter(sw); myDataList.RenderControl(tw); Response.Write(sb.ToString()); Response.End(); The problem is that WCF Service times out for large amount of data (about 5000 rows) and the result set is null. When I debug the service, I can see the window for saving/opening the excel sheet appear before the service returns the result and hence the excel sheet is always empty. Please help me figure this out.

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  • Import Excel 2007 into SQL 2000 using Classic ASP and ADO

    - by jeff
    I have the following code from a legacy app which currently reads from an excel 2003 spreadsheet on a server, but I need this to run from my machine which uses excel 2007. When I debug on my machine ADO does not seem to be reading the spreadsheet. I have checked all file paths etc. and location of spreadsheet that is all fine. I've heard that you cannot use the jet db engine for excel 2007 anymore? Can someone confirm this? What do I need to do to get this to work? Please help! set obj_conn = Server.CreateObject("ADODB.Connection") obj_conn.Open "Provider=Microsoft.Jet.OLEDB.4.0;" & _ "Data Source=" & Application("str_folder") & "CNS43.xls;" & _ "Extended Properties=""Excel 8.0;""" set obj_rs_cns43 = Server.CreateObject("ADODB.RecordSet") obj_rs_cns43.ActiveConnection = obj_conn obj_rs_cns43.CursorType = 3 obj_rs_cns43.LockType = 2 obj_rs_cns43.Source = "SELECT * FROM [CNS43$]" obj_rs_cns43.Open

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  • Automation Error upon running VBA script in Excel

    - by brohjoe
    Hi guys, I'm getting an Automation error upon running VBA code in Excel 2007. I'm attempting to connect to a remote SQL Server DB and load data to from Excel to SQL Server. The error I get is, "Run-time error '-2147217843(80040e4d)': Automation error". I checked out the MSDN site and it suggested that this may be due to a bug associated with the sqloledb provider and one way to mitigate this is to use ODBC. Well I changed the connection string to reflect ODBC provider and associated parameters and I'm still getting the same error. Here is the code with ODBC as the provider: Dim cnt As ADODB.Connection Dim rst As ADODB.Recordset Dim stSQL As String Dim wbBook As Workbook Dim wsSheet As Worksheet Dim rnStart As Range Public Sub loadData() 'This was set up using Microsoft ActiveX Data Components version 6.0. 'Create ADODB connection object, open connection and construct the connection string object. Set cnt = New ADODB.Connection cnt.ConnectionString = _ "Driver={SQL Server}; Server=onlineSQLServer2010.foo.com; Database=fooDB Uid=logonalready;Pwd='helpmeOB1';" cnt.Open On Error GoTo ErrorHandler 'Open Excel and run query to export data to SQL Server. strSQL = "SELECT * INTO SalesOrders FROM OPENDATASOURCE('Microsoft.ACE.OLEDB.12.0', & _ "'Data Source=C:\Database.xlsx; Extended Properties=Excel 12.0')...[SalesOrders$]" cnt.Execute (strSQL) 'Error handling. ErrorExit: 'Reclaim memory from the connection objects Set rst = Nothing Set cnt = Nothing Exit Sub ErrorHandler: MsgBox Err.Description, vbCritical Resume ErrorExit 'clean up and reclaim memory resources. cnt.Close If CBool(cnt.State And adStateOpen) Then Set rst = Nothing Set cnt = Nothing End If End Sub

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  • Automation Error when exporting Excel data to SQL Server

    - by brohjoe
    I'm getting an Automation error upon running VBA code in Excel 2007. I'm attempting to connect to a remote SQL Server DB and load data to from Excel to SQL Server. The error I get is, "Run-time error '-2147217843(80040e4d)': Automation error". I checked out the MSDN site and it suggested that this may be due to a bug associated with the sqloledb provider and one way to mitigate this is to use ODBC. Well I changed the connection string to reflect ODBC provider and associated parameters and I'm still getting the same error. Here is the code with ODBC as the provider: Dim cnt As ADODB.Connection Dim rst As ADODB.Recordset Dim stSQL As String Dim wbBook As Workbook Dim wsSheet As Worksheet Dim rnStart As Range Public Sub loadData() 'This was set up using Microsoft ActiveX Data Components version 6.0. 'Create ADODB connection object, open connection and construct the connection string object. Set cnt = New ADODB.Connection cnt.ConnectionString = "Driver={SQL Server}; Server=onlineSQLServer2010.foo.com; Database=fooDB;Uid=logonalready;Pwd='helpmeOB1';" cnt.Open On Error GoTo ErrorHandler 'Open Excel and run query to export data to SQL Server. strSQL = "SELECT * INTO SalesOrders FROM OPENDATASOURCE('Microsoft.ACE.OLEDB.12.0'," & _ "'Data Source=C:\Database.xlsx; Extended Properties=Excel 12.0')...[SalesOrders$]" cnt.Execute (strSQL) 'Error handling. ErrorExit: 'Reclaim memory from the connection objects Set rst = Nothing Set cnt = Nothing Exit Sub ErrorHandler: MsgBox Err.Description, vbCritical Resume ErrorExit 'clean up and reclaim memory resources. If CBool(cnt.State And adStateOpen) Then Set rst = Nothing Set cnt = Nothing cnt.Close End If End Sub

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  • Query MySQL data from Excel (or vice-versa)

    - by Charles
    I'm trying to automate a tedious problem. I get large Excel (.xls or .csv, whatever's more convenient) files with lists of people. I want to compare these against my MySQL database.* At the moment I'm exporting MySQL tables and reading them from an Excel spreadsheet. At that point it's not difficult to use =LOOKUP() and such commands to do the work I need, and of course the various text processing I need to do is easy enough to do in Excel. But I can't help but think that this is more work than it needs to be. Is there some way to get at the MySQL data directly from Excel? Alternately, is there a way I could access a reasonably large (~10k records) csv file in a sql script? This seems to be rather basic, but I haven't managed to make it work so far. I found an ODBC connection for MySQL but that doesn't seem to do what I need. In particular, I'm testing whether the name matches or whether any of four email addresses match. I also return information on what matched for the benefit of the next person to use the data, something like "Name 'Bob Smith' not found, but 'Robert Smith' matches on email address robert.smith@foo".

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  • Implementation of "Automatic Lightweight Migration" for Core Data (iPhone)

    - by RickiG
    Hi I would like to make my app able to do an automatic lightweight migration when I add new attributes to my core data model. In the guide from Apple this is the only info on the subject I could find: Automatic Lightweight Migration To request automatic lightweight migration, you set appropriate flags in the options dictionary you pass in addPersistentStoreWithType:configuration:URL:options:error:. You need to set values corresponding to both the NSMigratePersistentStoresAutomaticallyOption and the NSInferMappingModelAutomaticallyOption keys to YES: NSError *error; NSURL *storeURL = <#The URL of a persistent store#>; NSPersistentStoreCoordinator *psc = <#The coordinator#>; NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption, [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil]; if (![psc addPersistentStoreWithType:<#Store type#> configuration:<#Configuration or nil#> URL:storeURL options:options error:&error]) { // Handle the error. } My NSPersistentStoreCoordinator is initialized in this way: - (NSPersistentStoreCoordinator *)persistentStoreCoordinator { if (persistentStoreCoordinator != nil) { return persistentStoreCoordinator; } NSURL *storeUrl = [NSURL fileURLWithPath: [[self applicationDocumentsDirectory] stringByAppendingPathComponent: @"FC.sqlite"]]; NSError *error = nil; persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]]; if (![persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeUrl options:nil error:&error]) { NSLog(@"Unresolved error %@, %@", error, [error userInfo]); abort(); } return persistentStoreCoordinator; } I am having trouble seeing where and how I should add the Apple code to get the Automatic Lightweight Migration working?

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  • How to distribute an offline cube for excel

    - by Mike M
    I have the following scenario. A cube created in SSAS 2008. I can connected to this cube via Excel. I can create an offline cube file. I can connect to this offline cube file. Now, say I want to email this excel file along with the cube file so that another user can view it. I run into the problem that the connection path the offline cube is hard coded into the excel file. Its the same problem this person had. http://stackoverflow.com/questions/1253950/opening-offline-cube-from-another-machine Their solution was to just make sure the other user saved the cube in the same directory structure. I don't love that solution. I also came across this idea: http://www.pcreview.co.uk/forums/thread-948974.php I tried that, it errored out, but I am not an Excel VBA programmer and really have no idea if I even put the code in the right place. So anyway, anyone out there have any ideas about who to do this? If the VBA solution is the best, could someone give me some tips on where to actually put that code?

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  • Migrating a Large amount of data from old publishing site to new site

    - by tommizzle
    Hi, I am currently in the process of creating a new news/publishing site on the Movable Type platform. There are around 20 or so sites with 20,000+ rows of data to be moved/aggregated to ~8 sites (we have a number of location specific sites and are going to aggregate the content from these into 1 single site for each niche). We have discussed how to do this and came to the conclusion that it would probably be better to hire somebody to do it (I could probably do it, but i'm limited on time and am sure that a specialist would be more efficient). So my questions to you guys are: 1) What kind of skill set should we look for in an applicant? 2) There will be a large amount of input from our side... is getting somebody to work remotely out of the question? 3) How long would a task like this traditionally take (I know this question is very subjective, but an estimation would be awesome)? 4) Do you have any recommendations for firms who would be able to take on a large task like this? Thanks in advance, Tom

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  • Have no idea with python-excel read data file

    - by Protoss Reed
    I am a student and haven't a big expirence to do this work. So problem is next. I have a part of code: import matplotlib.pyplot as plt from pylab import * import cmath def sf(prompt): """ """ error_message = "Value must be integer and greater or equal than zero" while True: val = raw_input(prompt) try: val = float(val) except ValueError: print(error_message) continue if val <= 0: print(error_message) continue return val def petrogen_elements(): """Input and calculations the main parameters for pertogen elements""" print "Please enter Petrogen elements: \r" SiO2 = sf("SiO2: ") Al2O3= sf("Al2O3: ") Na2O = sf("Na2O: ") K2O = sf("K2O: ") petro = [SiO2,TiO2,Al2O3,] Sum = sum(petro) Alcal = Na2O + K2O TypeA lcal= Na2O / K2O Ka= (Na2O + K2O)/ Al2O3 print '-'*20, "\r Alcal: %s \r TypeAlcal: %s \ \r Ka: %s \r" % (Alcal, TypeAlcal,Ka,) petrogen_elements() So the problem is next. I have to load and read excel file and read all data in it. After that program have to calculate for example Alcaline, Type of Alcaline etc. Excel file has only this structure 1 2 3 4 5   1 name1 SiO2 Al2O3 Na2O K2O 2 32 12 0.21 0.1 3 name2 SiO2 Al2O3 Na2O K2O 4 45 8 7.54 5 5 name3 SiO2 Al2O3 Na2O K2O 6. … …. …. … … … All excel file has only 5 columns and unlimited rows. User has choice input data or import excel file. First part of work I have done but it stays a big part Finally I need to read all file and calculate the values. I would be so grateful for some advice

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  • Emailing an excel sheet with SSL in Python

    - by jakecar
    Hi...this is my first post so let me know if there are any common courtesies I should know about. I just started programming 8 months ago, so I am fairly new. I have been doing some projects to get better. A project I'm working on now creates an Excel sheet from inputted data. It's in Python, which I just started learning a couple of weeks ago. I'm attempting to embed part of this Excel sheet into an email, sent from my school address. I have spent hours looking this up, and to no avail. There are two problems I am asking for help with: 1) I have figured out how to send an email from my GMail account, but not from my school address. My school email uses SSL port 465, which I have tried to use, but to no avail. Unfortunately, I have been having a problem setting up outgoing email for this account on my iPhone as well. It may be related? Does anyone know of common issues relating to outgoing email with SSL and Python? 2) Excel has an option of saving a sheet as a HTML. When doing so, I copy and pasted the HTML source and emailed it as an attachment. Unfortunately, the colored text did not transfer over. Does anyone know of a better way of using Python to send an excel sheet embedded in an email? Thanks for your help!

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  • Using Excel VBA to Create SQL Tables

    - by user307655
    Hi All, I am trying to use Excel VBA to automate the creation of a SQL table in an existing SQL Database. I have come across the following code on this side. Private Sub CreateDatabaseFromExcel() Dim dbConnectStr As String Dim Catalog As Object Dim cnt As ADODB.Connection Dim dbPath As String Dim tblName As String 'Set database name in the Excel Sheet dbPath = ActiveSheet.Range("B1").Value 'Database Name tblName = ActiveSheet.Range("B2").Value 'Table Name dbConnectStr = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & dbPath & ";" 'Create new database using name entered in Excel Cell ("B1") Set Catalog = CreateObject("ADOX.Catalog") Catalog.Create dbConnectStr Set Catalog = Nothing 'Connect to database and insert a new table Set cnt = New ADODB.Connection With cnt .Open dbConnectStr .Execute "CREATE TABLE tblName ([BankName] text(50) WITH Compression, " & _ "[RTNumber] text(9) WITH Compression, " & _ "[AccountNumber] text(10) WITH Compression, " & _ "[Address] text(150) WITH Compression, " & _ "[City] text(50) WITH Compression, " & _ "[ProvinceState] text(2) WITH Compression, " & _ "[Postal] text(6) WITH Compression, " & _ "[AccountAmount] decimal(6))" End With Set cnt = Nothing End Sub However i can't successfully get it to work? What I am trying to do is actually use Excel to create a table not a database? The database already exists. I would just like to create a new table. The name of the table will be referenced from cell A1 in Sheet 1. Can somebody please help. Thanks Regards Gerard

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  • MS Office Excel Ribbon - Cannot change/hide Editing group in Home tab

    - by A9S6
    I have a .net addin for Excel. The addin creates the Ribbon UI for Excel 2007 and re-purposes some existing commands such as Cut, Copy, Paste, Sort etc. For Cut, Copy and Paste I am just overriding their OnAction value to call my own procedure when the buttons are clicked. But for Sort, Sort Asc and Sort Desc commands the case is a little different. When either of the Sort, Sort Asc or Sort Desc buttons are clicked, I want to get notified and then call the default functionality. This was possible in Excel 2003 commandsbars by calling the Execute() method on the CommandBarControl. In Excel 2007, there is a ExecuteMso() method to programmatically click a ribbon element but when the OnAction is overridden, this ExecuteMso() method just executes my own procedure and not the default functionality of that button. So I thought that I will HIDE the Sort buttons in the "Editing" group in Home tab and add my own Sort, Sort Asc and Sort Desc buttons to it. The buttons will call into my procedure first from where I will call the default behavior. Now the problem is that I am unable to change/hide the Editing group (idMso="GroupEditing"). Is this built-in group not editable? I can however HIDE the Clipboard and other groups(but can't add buttons to them). <?xml version="1.0" encoding="UTF-8" standalone="yes"?> <customUI xmlns="http://schemas.microsoft.com/office/2006/01/customui"> <ribbon> <tabs> <tab idMso="TabHome"> <group idMso="GroupEditing" visible="false" /> </tab> </tabs> </ribbon> </customUI>

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  • Spring Data Neo4J @Indexed(unique = true) not working

    - by Markus Lamm
    I'm new to Neo4J and I have, probably an easy question. There're NodeEntitys in my application, a property (name) is annotated with @Indexed(unique = true) to achieve the uniqueness like I do in JPA with @Column(unique = true). My problem is, that when I persist an entity with a name that already exists in my graph, it works fine anyway. But I expected some kind of exception here...?! Here' s an overview over basic my code: @NodeEntity public abstract class BaseEntity implements Identifiable { @GraphId private Long entityId; ... } public class Role extends BaseEntity { @Indexed(unique = true) private String name; ... } public interface RoleRepository extends GraphRepository<Role> { Role findByName(String name); } @Service public class RoleServiceImpl extends BaseEntityServiceImpl<Role> implements { private RoleRepository repository; @Override @Transactional public T save(final T entity) { return getRepository().save(entity); } } And this is my test: @Test public void testNameUniqueIndex() { final List<Role> roles = Lists.newLinkedList(service.findAll()); final String existingName = roles.get(0).getName(); Role newRole = new Role.Builder(existingName).build(); newRole = service.save(newRole); } That's the point where I expect something to go wrong! How can I ensure the uniqueness of a property, without checking it for myself?? THANKS IN ADVANCE FOR ANY IDEAS!! P.S.: I'm using neo4j 1.8.M07, spring-data-neo4j 2.1.0.BUILD-SNAPSHOT and Spring 3.1.2.RELEASE.

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  • Silverlight Export Datagrid to Excel (without roundtrip)

    - by kirkktx
    I've got a silverlight 2 app with a Datagrid and a button for exporting it to Excel by making a trip back to the server. I can create an HTML string representing the datagrid. I'd like to attach this string to an html element, setting MIME type=application/vnd.ms-excel and have a prompt show up asking if I'd like to open or save the xls file. After all if ASP can do this ... <% The main feature of this technique is that %> <% you have to change Content type to ms-excel.%> Response.ContentType = "application/vnd.ms-excel" <TABLE> <TR><TD>2</TD></TR> <TR><TD>3</TD></TR> <TR><TD>=SUM(A1:A2)</TD></TR> </TABLE> ... it seems like I should be able to do something similar from within Silverlight, pushing it onto the HTML DOM. Any suggestions greatly appreciated!

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  • Transfering data from Excel to dataGridView

    - by Panecillo
    I have a problem when I want to transfer data from Excel to dataGridView in C#. My Excel's column has numeric and alphanumeric values. But for example, if the column has 3 numbers and 2 alphanumeric values then only the numbers are shown in the dataGridView, and vice versa. Why aren't all the values shown? The next is what happen: Excel's Column: DataGridView's Column: 45654 45654 P745K 31233 31233 23111 23111 45X2Y Here is my code to load the dataGridView: string connectionString = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=D:\test.xls;Extended Properties=""Excel 8.0;HDR=YES;"""; DbProviderFactory factory = DbProviderFactories.GetFactory("System.Data.OleDb"); DbDataAdapter adapter = factory.CreateDataAdapter(); DbCommand selectCommand = factory.CreateCommand(); selectCommand.CommandText = "SELECT * FROM [sheet1$]"; DbConnection connection = factory.CreateConnection(); connection.ConnectionString = connectionString; selectCommand.Connection = connection; adapter.SelectCommand = selectCommand; data = new DataSet(); adapter.Fill(data); dataGridView1.DataSource = data.Tables[0].DefaultView; I hope I explained it well. Sorry my bad english. Thanks.

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  • How do you cancel an external git diff?

    - by v2k
    I've got vim setup as my external diff tool: [diff] external = git_diff_wrapper !/bin/sh vimdiff "$2" "$5" Say I have 300 files that have been modified; via bash, I type "git diff". It launches 300 vimdiffs sequentially, how do I abort it?

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  • Strange error inserting new relationship data in core-data

    - by michael
    My app will allow users to create a personalised list of events from a large list of events. I have a table view which simply displays these events, tapping on one of them takes the user to the event details view, which has a button "add to my events". In this detailed view I own the original event object, retrieved via an NSFetchedResultsController and passed to the detailed view (via a table cell, the same as the core data recipes sample). I have no trouble retrieving/displaying information from this "event". I am then trying to add it to the list of MyEvents represented by a one to many (inverse) relationship: This code: NSManagedObjectContext *context = [event managedObjectContext]; MyEvents *myEvents = (MyEvents *)[NSEntityDescription insertNewObjectForEntityForName:@"MyEvents" inManagedObjectContext:context]; [myEvents addEventObject:event];//ERROR And this code (suggested below): //would this add to or overwrite the "list" i am attempting to maintain NSManagedObjectContext *context = [event managedObjectContext]; MyEvents *myEvents = (MyEvents *)[NSEntityDescription insertNewObjectForEntityForName:@"MyEvents" inManagedObjectContext:context]; NSMutableSet *myEvent = [myEvents mutableSetValueForKey:@"event"]; [myEvent addObject:event]; //ERROR Bot produce (at the line indicated by //ERROR): *** -[NSComparisonPredicate evaluateWithObject:]: message sent to deallocated instance Seems I may have missed something fundamental. I cant glean any more information through the use of debugging tools, with my knowledge of them. 1) Is this a valid way to compile and store an editable list like this? 2) Is there a better way? 3) What could possibly be the deallocated instance in error? -- I have now modified the Event entity to have a to-many relationship called "myEvents" which referrers to itself. I can add Events to this fine, and logging the object shows the correct memory addresses appearing for the relationship after a [event addMyEventObject:event];. The same failure happens right after this however. I am still at a loss to understand what is going wrong. This is the backtrace #0 0x01f753a7 in ___forwarding___ () #1 0x01f516c2 in __forwarding_prep_0___ () #2 0x01c5aa8f in -[NSFetchedResultsController(PrivateMethods) _preprocessUpdatedObjects:insertsInfo:deletesInfo:updatesInfo:sectionsWithDeletes:newSectionNames:treatAsRefreshes:] () #3 0x01c5d63b in -[NSFetchedResultsController(PrivateMethods) _managedObjectContextDidChange:] () #4 0x0002e63a in _nsnote_callback () #5 0x01f40005 in _CFXNotificationPostNotification () #6 0x0002bef0 in -[NSNotificationCenter postNotificationName:object:userInfo:] () #7 0x01bbe17d in -[NSManagedObjectContext(_NSInternalNotificationHandling) _postObjectsDidChangeNotificationWithUserInfo:] () #8 0x01c1d763 in -[NSManagedObjectContext(_NSInternalChangeProcessing) _createAndPostChangeNotification:withDeletions:withUpdates:withRefreshes:] () #9 0x01ba25ea in -[NSManagedObjectContext(_NSInternalChangeProcessing) _processRecentChanges:] () #10 0x01bdfb3a in -[NSManagedObjectContext processPendingChanges] () #11 0x01bd0957 in _performRunLoopAction () #12 0x01f4d252 in __CFRunLoopDoObservers () #13 0x01f4c65f in CFRunLoopRunSpecific () #14 0x01f4bc48 in CFRunLoopRunInMode () #15 0x0273878d in GSEventRunModal () #16 0x02738852 in GSEventRun () #17 0x002ba003 in UIApplicationMain () Cheers.

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  • Dealing with external processes

    - by Jesse Aldridge
    I've been working on a gui app that needs to manage external processes. Working with external processes leads to a lot of issues that can make a programmer's life difficult. I feel like maintenence on this app is taking an unacceptably long time. I've been trying to list the things that make working with external processes difficult so that I can come up with ways of mitigating the pain. This kind of turned into a rant which I thought I'd post here in order to get some feedback and to provide some guidance to anybody thinking about sailing into these very murky waters. Here's what I've got so far: Output from the child can get mixed up with output from the parent. This can make both outputs misleading and hard to read. It can be hard to tell what came from where. It becomes harder to figure out what's going on when things are asynchronous. Here's a contrived example: import textwrap, os, time from subprocess import Popen test_path = 'test_file.py' with open(test_path, 'w') as file: file.write(textwrap.dedent(''' import time for i in range(3): print 'Hello %i' % i time.sleep(1)''')) proc = Popen('python -B "%s"' % test_path) for i in range(3): print 'Hello %i' % i time.sleep(1) os.remove(test_path) I guess I could have the child process write its output to a file. But it can be annoying to have to open up a file every time I want to see the result of a print statement. If I have code for the child process I could add a label, something like print 'child: Hello %i', but it can be annoying to do that for every print. And it adds some noise to the output. And of course I can't do it if I don't have access to the code. I could manually manage the process output. But then you open up a huge can of worms with threads and polling and stuff like that. A simple solution is to treat processes like synchronous functions, that is, no further code executes until the process completes. In other words, make the process block. But that doesn't work if you're building a gui app. Which brings me to the next problem... Blocking processes cause the gui to become unresponsive. import textwrap, sys, os from subprocess import Popen from PyQt4.QtGui import * from PyQt4.QtCore import * test_path = 'test_file.py' with open(test_path, 'w') as file: file.write(textwrap.dedent(''' import time for i in range(3): print 'Hello %i' % i time.sleep(1)''')) app = QApplication(sys.argv) button = QPushButton('Launch process') def launch_proc(): # Can't move the window until process completes proc = Popen('python -B "%s"' % test_path) proc.communicate() button.connect(button, SIGNAL('clicked()'), launch_proc) button.show() app.exec_() os.remove(test_path) Qt provides a process wrapper of its own called QProcess which can help with this. You can connect functions to signals to capture output relatively easily. This is what I'm currently using. But I'm finding that all these signals behave suspiciously like goto statements and can lead to spaghetti code. I think I want to get sort-of blocking behavior by having the 'finished' signal from QProcess call a function containing all the code that comes after the process call. I think that should work but I'm still a bit fuzzy on the details... Stack traces get interrupted when you go from the child process back to the parent process. If a normal function screws up, you get a nice complete stack trace with filenames and line numbers. If a subprocess screws up, you'll be lucky if you get any output at all. You end up having to do a lot more detective work everytime something goes wrong. Speaking of which, output has a way of disappearing when dealing external processes. Like if you run something via the windows 'cmd' command, the console will pop up, execute the code, and then disappear before you have a chance to see the output. You have to pass the /k flag to make it stick around. Similar issues seem to crop up all the time. I suppose both problems 3 and 4 have the same root cause: no exception handling. Exception handling is meant to be used with functions, it doesn't work with processes. Maybe there's some way to get something like exception handling for processes? I guess that's what stderr is for? But dealing with two different streams can be annoying in itself. Maybe I should look into this more... Processes can hang and stick around in the background without you realizing it. So you end up yelling at your computer cuz it's going so slow until you finally bring up your task manager and see 30 instances of the same process hanging out in the background. Also, hanging background processes can interefere with other instances of the process in various fun ways, such as causing permissions errors by holding a handle to a file or someting like that. It seems like an easy solution to this would be to have the parent process kill the child process on exit if the child process didn't close itself. But if the parent process crashes, cleanup code might not get called and the child can be left hanging. Also, if the parent waits for the child to complete, and the child is in an infinite loop or something, you can end up with two hanging processes. This problem can tie in to problem 2 for extra fun, causing your gui to stop responding entirely and force you to kill everything with the task manager. F***ing quotes Parameters often need to be passed to processes. This is a headache in itself. Especially if you're dealing with file paths. Say... 'C:/My Documents/whatever/'. If you don't have quotes, the string will often be split at the space and interpreted as two arguments. If you need nested quotes you can use ' and ". But if you need to use more than two layers of quotes, you have to do some nasty escaping, for example: "cmd /k 'python \'path 1\' \'path 2\''". A good solution to this problem is passing parameters as a list rather than as a single string. Subprocess allows you to do this. Can't easily return data from a subprocess. You can use stdout of course. But what if you want to throw a print in there for debugging purposes? That's gonna screw up the parent if it's expecting output formatted a certain way. In functions you can print one string and return another and everything works just fine. Obscure command-line flags and a crappy terminal based help system. These are problems I often run into when using os level apps. Like the /k flag I mentioned, for holding a cmd window open, who's idea was that? Unix apps don't tend to be much friendlier in this regard. Hopefully you can use google or StackOverflow to find the answer you need. But if not, you've got a lot of boring reading and frusterating trial and error to do. External factors. This one's kind of fuzzy. But when you leave the relatively sheltered harbor of your own scripts to deal with external processes you find yourself having to deal with the "outside world" to a much greater extent. And that's a scary place. All sorts of things can go wrong. Just to give a random example: the cwd in which a process is run can modify it's behavior. There are probably other issues, but those are the ones I've written down so far. Any other snags you'd like to add? Any suggestions for dealing with these problems?

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