I am using the h5py python package to read files in HDF5 format. (e.g. somefile.h5) I would like to write the contents of a dataset to a text file. For example, I would like to create a text file with the following contents: 1,20,31,75,142,324,78,12,3,90,8,21,1 I am able to access the dataset in python using this code: import h5py f = h5py.File('/Users/Me/Desktop/thefile.h5', 'r') group = f['/level1/level2/level3'] dset = group['dsetname'] My naive approach is too slow, because my dataset has over 20000 entries: # write all values to file for index in range(len(dset)): # do not add comma after last value if index == len(dset)-1: txtfile.write(repr(dset[index])) else: txtfile.write(repr(dset[index])+',') txtfile.close() return None Is there a faster way to write this to a file? Perhaps I could convert the dataset into a NumPy array or even a Python list, and then use some file-writing tool? (I could experiment with concatenating the values into a larger string before writing to file, but I'm hoping there's something entirely more elegant)