Question

I have the following Python code to write dependency files of a project. It works fine with Python 2.x, but while testing it with Python 3 it reports an error.

depend = None
if not nmake:
    depend = open(".depend", "a")
dependmak = open(".depend.mak", "a")
depend = open(".depend", "a")
print >>depend, s,

Here is the error:

Traceback (most recent call last):
  File "../../../../config/makedepend.py", line 121, in <module>
    print >>depend, s,
    TypeError: unsupported operand type(s) for >>:
      'builtin_function_or_method' and '_io.TextIOWrapper'

What is the best way to get this working with Python 2.x and 3.x?

Answer 1

In Python 3 the print statement has become a function. The new syntax looks like this:

print(s, end="", file=depend)

This breaking change in Python 3 means that it is not possible to use the same code in Python 2 and 3 when writing to a file using the print statement/function. One possible option would be to use depend.write(s) instead of print.

Update: J.F. Sebastian correctly points out that you can use from __future__ import print_function in your Python 2 code to enable the Python 3 syntax. That would be an excellent way to use the same code across different Python versions.