What's the Pythonic way to go about reading files line by line of the two methods below?
with open('file', 'r') as f:
for line in f:
print line
or
with open('file', 'r') as f:
for line in f.readlines():
print line
Or is there something I'm missing?
File handles are their own iterators (specifically, they implement the iterator protocol) so
with open('file', 'r') as f:
for line in f:
# code
Is the preferred usage. f.readlines() returns a list of lines, which means absorbing the entire file into memory -> generally ill advised, especially for large files.
It should be pointed out that I agree with the sentiment that context managers are worthwhile, and have included one in my code example.
Of the two you presented, the first is recommended practice. As pointed out in the comments, any solution (like that below) which doesn't use a context manager means that the file is left open, which is a bad idea.
Original answer which leaves dangling file handles so shouldn't be followed
However, if you don't need f for any purpose other than reading the lines, you can just do:
for line in open('file', 'r'):
print line
theres' no need for .readlines() method call.
PLUS: About with statement
The execution behavior of with statement is as commented below,
with open("xxx.txt",'r') as f:
// now, f is an opened file in context
for line in f:
// code with line
pass // when control exits *with*, f is closed
print f // if you print, you'll get <closed file 'xxx.txt'>
