I want to read a huge file in my code. Is read() or readline() faster for this. How about the loop:
for line in fileHandle
For a text file just iterating over it with a
for loop is almost always the way to go. Never mind about speed, it is the cleanest.
In some versions of python
readline() really does just read a single line while the
for loop reads large chunks and splits them up into lines so it may be faster. I think that more recent versions of Python use buffering also for
readline() so the performance difference will be minuscule (
for is probably still microscopically faster because it avoids a method call). However choosing one over the other for performance reasons is probably premature optimisation.
Edit to add: I just checked back through some Python release notes. Python 2.5 said:
It’s now illegal to mix iterating over a file with for line in file and calling the file object’s read()/readline()/readlines() methods.
Python 2.6 introduced TextIOBase which supports both iterating and
Python 2.7 fixed interleaving