The difference between sys.stdout.write and print?


Question

Are there situations in which sys.stdout.write() is preferable to print?

(Examples: better performance; code that makes more sense)

1
330
11/17/2017 4:55:36 PM

Accepted Answer

print is just a thin wrapper that formats the inputs (modifiable, but by default with a space between args and newline at the end) and calls the write function of a given object. By default this object is sys.stdout, but you can pass a file using the "chevron" form. For example:

print >> open('file.txt', 'w'), 'Hello', 'World', 2+3

See: https://docs.python.org/2/reference/simple_stmts.html?highlight=print#the-print-statement


In Python 3.x, print becomes a function, but it is still possible to pass something other than sys.stdout thanks to the fileargument.

print('Hello', 'World', 2+3, file=open('file.txt', 'w'))

See https://docs.python.org/3/library/functions.html#print


In Python 2.6+, print is still a statement, but it can be used as a function with

from __future__ import print_function

Update: Bakuriu commented to point out that there is a small difference between the print function and the print statement (and more generally between a function and a statement).

In case of an error when evaluating arguments:

print "something", 1/0, "other" #prints only something because 1/0 raise an Exception

print("something", 1/0, "other") #doesn't print anything. The function is not called
261
5/17/2019 8:57:24 PM

print first converts the object to a string (if it is not already a string). It will also put a space before the object if it is not the start of a line and a newline character at the end.

When using stdout, you need to convert the object to a string yourself (by calling "str", for example) and there is no newline character.

So

print 99

is equivalent to:

import sys
sys.stdout.write(str(99) + '\n')

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