I'm new to Python and I'm trying to declare a variable and print its value.
This is my code:
#!C:\Python32\python.exe
import sys
import os
import cgi
import cgitb
cgitb.enable()
a = 5
print(a)-------------------------> My doubt is in this line
But one of my friends writes that line as print a. In his Python, it is printing that value, but in my case it is showing as "Invalid Syntax". Why is this happening?
In Python 2, print isn't a function, but a keyword. The parentheses therefore don't matter and print 'foo' works along with print('foo').
Python 3 made print into a function, which has to be called with parameters: print('foo'). Calling it as print 'foo' will not work anymore.
Since you're getting errors when using print as a keyword, you're using Python 3. You have to use print as a function, just like you did. Your friend is using Python 2, which works both ways.
Python 3 and Python 2 are similar, but there are a few major differences that you should read about if you're planning on collaborating with someone who uses a different version of Python: http://docs.python.org/py3k/whatsnew/3.0.html
Since you're in Python 3, print is a function, so you call it as: print(a). In Python 2 (what your friend is using), you can leave off the parenthesis, and call it as just: print a, but this won't work in the future, so your way is correct.
Also, your version (print(a)) will work on both Python 3 and Python 2, since extra parenthesis are ignored as long as they match. I recommend always writing it in Python 3 style, since it works in both. You can make this explicit and required by using the (somewhat magical) __future__ module:
from __future__ import print_function
Having print as a function causes some other differences, since in Python 3, you can set a variable to point to print, or pass it as an argument to a function:
a = print
a('magic') # prints 'magic'
def add_and_call(func, num):
num += 1
func(num)
add_and_call(print, 1) # prints 2
