Python – Where is ‘from future import braces’ Code

pythonpython-2.7python-internals

I was wondering what is exactly the code that gets executed on the command:

>>> from __future__ import braces
SyntaxError: not a chance

Since Python is open-sourced, I opened C:\Python27\Lib\__future__.py and looked.
Surprisingly, I found nothing there that handles importing the braces module.

So, my question is, where is the code that handles this? What happens when I run that command?

Best Answer

The code is in future.c:

future_check_features(PyFutureFeatures *ff, stmt_ty s, const char *filename)
...
  else if (strcmp(feature, "braces") == 0) {
    PyErr_SetString(PyExc_SyntaxError,
        "not a chance");
    PyErr_SyntaxLocation(filename, s->lineno);
    return 0;
  }

Related Solutions

Python – What Does ‘from future import barry_as_FLUFL’ Do?

It's related to PEP 0401: BDFL Retirement

Barry refers to Barry Warsaw, a well-known Python developer. The from __future__ import barry_as_FLUFL basically replaces the != operator with <>.

Python – What is future in Python and How to Use It

With __future__ module's inclusion, you can slowly be accustomed to incompatible changes or to such ones introducing new keywords.

E.g., for using context managers, you had to do from __future__ import with_statement in 2.5, as the with keyword was new and shouldn't be used as variable names any longer. In order to use with as a Python keyword in Python 2.5 or older, you will need to use the import from above.

Another example is

from __future__ import division
print 8/7  # prints 1.1428571428571428
print 8//7 # prints 1

Without the __future__ stuff, both print statements would print 1.

The internal difference is that without that import, / is mapped to the __div__() method, while with it, __truediv__() is used. (In any case, // calls __floordiv__().)

Apropos print: print becomes a function in 3.x, losing its special property as a keyword. So it is the other way round.

>>> print

>>> from __future__ import print_function
>>> print
<built-in function print>
>>>

Best Answer

Related Solutions

Python – What Does ‘from __future__ import barry_as_FLUFL’ Do?

Python – What is __future__ in Python and How to Use It

Related Question

Python – What Does ‘from future import barry_as_FLUFL’ Do?

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