is compatibility builtins broken?

[Chris Smith]

Am I doing something wrong here when running Python 2?

>>> from sympy.core.compatibility import builtins
>>> from builtins import type
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: No module named builtins

/c

[SHUBHAM JHA]

Hi Chris,

I am using version 1.5-dev

In [2]: from sympy.core.compatibility import builtins
In [3]: from builtins import type
In [4]:

Also,

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[Oscar Benjamin]

There are two possible wrong things:

1) On Python 2 the module is called __builtin__:

>>> import __builtin__
>>> __builtin__.map
<built-in function map>

2) You've imported the name builtins so that it is available as a name
in the current global namespace. That does not mean that a subsequent
import statement will import from the resulting module object. An
import statement never looks at the names in the current namespace to
find anything. You can however do

import sympy.core.compatbility.builtins as builtins
builtins.type

Or

from sympy.core.compatibility.builtins import type

Not sure what you're aiming for but there is a hacky way to do it:

sys.modules['builtins'] = builtins

--
Oscar

[Chris Smith]

None of them work

>>> import sympy.core.compatibility.builtins as builtins

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

ImportError: No module named builtins

>>> from sympy.core.compatibility.builtins import type

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

ImportError: No module named builtins

>>> sys.modules['builtins']=__builtin__

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

NameError: name '__builtin__' is not defined

but

>>> from __builtin__ import type

>>> 'builtins' in dir()

True

>>> builtins

<module '__builtin__' (built-in)>

>>> from builtins import type

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

ImportError: No module named builtins

[Vishesh Mangla]

What do these builtins ought to be doing?

 

Sent from Mail for Windows 10

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[Isuru Fernando]

You can do,

>>> from sympy.core.compatibility import builtins
>>> type = builtins.type

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[Oscar Benjamin]

On Wed, 8 May 2019 at 22:38, Chris Smith <smi...@gmail.com> wrote:
>
> None of them work

That's what I get for not trying them out!

> >>> import sympy.core.compatibility.builtins as builtins
> Traceback (most recent call last):
> File "<stdin>", line 1, in <module>
> ImportError: No module named builtins
>
> >>> from sympy.core.compatibility.builtins import type
> Traceback (most recent call last):
> File "<stdin>", line 1, in <module>
> ImportError: No module named builtins

Yes that's because there is no builtins module in the compatibility
package. In fact compatibility is a module not a package.

> >>> sys.modules['builtins']=__builtin__
> Traceback (most recent call last):
> File "<stdin>", line 1, in <module>
> NameError: name '__builtin__' is not defined

This will work if you have imported __builtin__ first:

>>> import __builtin__
>>> import sys
>>> sys.modules['builtins'] = __builtin__
>>> import builtins

--
Oscar

[Aaron Meurer]

What is this for? We shouldn't be monkey-patching sys.modules in library code.

Aaron Meurer

>
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[Chris Smith]

builtins is in core.compatibility and it doesn't seem to work for me.

The issue will go away when we drop Py 2.7...or sooner if someone can figure out what's wrong.

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[Aaron Meurer]

This works for me:

Python 2.7.14 | packaged by conda-forge | (default, Dec 9 2017, 16:31:12)
[GCC 4.2.1 Compatible Apple LLVM 6.1.0 (clang-602.0.53)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from sympy.core.compatibility import builtins
>>> builtins.type
<type 'type'>

Aaron Meurer

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[Chris Smith]

Hmm - yes, that works for me, too. But in Py3 you can do 'from builtins import type' -- is the only way to do that in 2 is to use monkey patching?

/c

[Aaron Meurer]

In Python 2 builtins was called called __builtin__. That's why it's in
the compatibility module (not to be confused with __builtins__, which
is a different thing, hence the rename). You could just as well write

try:
# Python 3
from builtins import type
except ImportError:
# Python 2
from __builtin__ import type

but the whole point of the SymPy compatibility module is to isolate
such 2/3 compatibility code into one place. So it's better to do

from sympy.core.compatibility import builtins
builtins.type

There's also another possible level of confusion here which is that if
you have the 'future' package installed in your Python 2 environment,
it automatically adds a builtins module to the standard library. So in
that case, 'from builtins import type' will work. But it shouldn't be
relied on for SymPy, because we do not have 'future' as a dependency
(and do not want to have it as one).

Aaron Meurer

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[Chris Smith]

Thanks for clarifying. I generally think of compatibility making it so whatever you do in Py3 you can do in Py2. In this case the common idiom is to reference a builtin from its module (builtins.foo) rather than to try import foo from builtins (which works with Py3 but not with Py2 *with the same name*).

/c