In C, it is considered bad practice to call strlen like this:

for ( i = 0; strlen ( str ) != foo; i++ )
{
    // stuff
}

The reason, of course, is that it is inefficient since it "counts" the characters in a string multiple times.

However, in Python, I see code like this quite often:

for i in range ( 0, len ( list ) ):
    # stuff

Is this bad practice? Should I store the result of len() in a variable and use that?