python无效语法错误：打印

Question

I try to write my first python program. But the print function is very special. I tried to write :

print ("success!")

very normal. but IDLE remind me that the code is wrong and "print" has been red. What should I do?

Answer 1

I think you are just seeing IDLE's syntax-highlighting feature. Keywords (and function names, variables etc.) are given different colours, in order to make the code easier to read (and spot errors like missing brackets etc.):

If you are seeing the same as this:

Then, you have nothing to worry about

Answer 2

Assuming this isn't just IDLE's syntax highlighting (hard to tell without the code in question)...

The reason for this odd behaviour has to do with a major change that was made in Python 3. In Python 2, print is a keyword. In Python 3, print is a function.

This has a number of implications:

1. In Python3, print requires parentheses
2. In Python2, print does not require parentheses by default
3. In Python2, print cannot be overridden by default (you cannot change what print does)
4. In Python3, print can be shadowed in a module, providing different behaviour for one application or another.

Now, what this means is that the syntax by default is different, but the good news is you can get the same syntax on both by putting as the first line in your module:

from __future__ import print_function

As a side note, this is a good idea since it ensures the same code will run on Python 2.7 and 3. So I add to all my Python modules these days:

from __future__ import print_function, division

(adding division there is good practice because of the way the division operator changed.)

Answer 3

问题可能出现在print出现在检查中的行中的任何地方，例如，如果您有正确的缩进