Why is parenthesis in print voluntary in Python 2.7?

In Python 2.x print is actually a special statement and not a function*.

This is also why it can't be used like: lambda x: print x

Note that (expr) does not create a Tuple (it results in expr), but , does. This likely results in the confusion between print (x) and print (x, y) in Python 2.7

(1)   # 1 -- no tuple Mister!(1,)  # (1,)(1,2) # (1, 2)1,2   # 1 2 -- no tuple and no parenthesis :) [See below for print caveat.]

However, since print is a special syntax statement/grammar construct in Python 2.x then, without the parenthesis, it treats the ,'s in a special manner - and does not create a Tuple. This special treatment of the print statement enables it to act differently if there is a trailing , or not.

Happy coding.

*This print behavior in Python 2 can be changed to that of Python 3:

from __future__ import print_function

It's all very simple and has nothing to do with forward or backward compatibility.

The general form for the print statement in all Python versions before version 3 is:

print expr1, expr2, ... exprn

(Each expression in turn is evaluated, converted to a string and displayed with a space between them.)

But remember that putting parentheses around an expression is still the same expression.

So you can also write this as:

print (expr1), (expr2), ... (expr3)

This has nothing to do with calling a function.

Here we have interesting side effect when it comes to UTF-8.

>> greek = dict( dog="σκύλος", cat="γάτα" )>> print greek['dog'], greek['cat']σκύλος γάτα>> print (greek['dog'], greek['cat'])('\xcf\x83\xce\xba\xcf\x8d\xce\xbb\xce\xbf\xcf\x82', '\xce\xb3\xce\xac\xcf\x84\xce\xb1')

The last print is tuple with hexadecimal byte values.