Python Pocket Reference, 3rd Edition

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Python Pocket Reference

apply( )-like call syntax

As of Python 2.0, special syntax can be used in function and

method call argument lists to achieve the same effect as an

apply() built-in function call. If args and kw are a tuple and a

dictionary, respectively, the following are equivalent:

apply(f, args, kw)

f(*args, **kw)

Both formats call function f with a positional arguments

sequence of

args and a keyword arguments dictionary of kw.

The latter format is intended to be symmetric with function

header arbitrary-argument syntax such as

def f(*args,

**kw):

. It is also more flexible, since it can be more easily

combined with positional and keyword arguments (e.g.,

f(1,2,foo=3,bar=4,*args,**kw)).

The print Statement

print [value [, value]* [,]]

print >> fileobj [, value [,value]* [,]]

print displays the printable representation of values on a

stdout stream (the current setting of sys.stdout) as well as

adds spaces between values. The trailing comma suppresses

the linefeed that is normally added at the end of a list.

Because

print simply calls the write method of the object

currently referenced by

sys.stdout, the following is equiva-

lent to

print X:

import sys

sys.stdout.write(str(X) + '\n')

To redirect print text to files or class objects, reassign sys.

stdout

to any object with a write method:

sys.stdout = open('log', 'a') # any object with a write()

print "Warning-bad spam!" # goes to the object's write()