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I have two files, and I want to perform some line-wise operation across both of them. (In other words, the first lines of each file correspond, as do the second, etc.) Now, I can think of a number of slightly cumbersome ways to iterate across both files simultaneously; however, this is Python, so I imagine that there is some syntactic shorthand.
In other words, is there some simple way to adapt the
for line in file: so that it pulls data from both files simultaneously?
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Steps Needed Steps used to open multiple files together in Python : Both the files are opened with open() method using different names for each. The contents of the files can be accessed using readline() method. Different read/write operations can be performed over the contents of these files.
You can loop through the list items by using a while loop. Use the len() function to determine the length of the list, then start at 0 and loop your way through the list items by referring to their indexes. Remember to increase the index by 1 after each iteration.
Python 2:
Use itertools.izip to join the two iterators.
from itertools import izip for line_from_file_1, line_from_file_2 in izip(open(file_1), open(file_2)): If the files are of unequal length, use izip_longest.
In Python 3, use zip and zip_longest instead. Also, use a with to open files, so that closing is handled automatically even in case of errors.
with open(file1name) as file1, open(file2name) as file2: for line1, line2 in zip(file1, file2): #do stuff You could try
for line1, line2 in zip(file1, file2): #do stuff Careful though, this loop will exit when the shorter file ends.
When using Python 2, itertools.izip is better for this sort of thing because it doesn't create a list.
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