What is an alternative to execfile in Python 3?

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What is an alternative to execfile in Python 3?

It seems they canceled in Python 3 all the easy way to quickly load a script by removing execfile()

Is there an obvious alternative I’m missing?

Asked By: R S

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Answer #1:

According to the documentation, instead of

execfile("./filename")

Use

exec(open("./filename").read())

See:

Answered By: Pedro Vagner

Answer #2:

You are just supposed to read the file and exec the code yourself. 2to3 current replaces

execfile("somefile.py", global_vars, local_vars)

as

with open("somefile.py") as f:
    code = compile(f.read(), "somefile.py", 'exec')
    exec(code, global_vars, local_vars)

(The compile call isn’t strictly needed, but it associates the filename with the code object making debugging a little easier.)

See:

Answered By: Benjamin Peterson

Answer #3:

While exec(open("filename").read()) is often given as an alternative to execfile("filename"), it misses important details that execfile supported.

The following function for Python3.x is as close as I could get to having the same behavior as executing a file directly. That matches running python /path/to/somefile.py.

def execfile(filepath, globals=None, locals=None):
    if globals is None:
        globals = {}
    globals.update({
        "__file__": filepath,
        "__name__": "__main__",
    })
    with open(filepath, 'rb') as file:
        exec(compile(file.read(), filepath, 'exec'), globals, locals)
# execute the file
execfile("/path/to/somefile.py")

Notes:

  • Uses binary reading to avoid encoding issues
  • Guaranteed to close the file (Python3.x warns about this)
  • Defines __main__, some scripts depend on this to check if they are loading as a module or not for eg. if __name__ == "__main__"
  • Setting __file__ is nicer for exception messages and some scripts use __file__ to get the paths of other files relative to them.
  • Takes optional globals & locals arguments, modifying them in-place as execfile does – so you can access any variables defined by reading back the variables after running.

  • Unlike Python2’s execfile this does not modify the current namespace by default. For that you have to explicitly pass in globals() & locals().

Answered By: ideasman42

Answer #4:

As suggested on the python-dev mailinglist recently, the runpy module might be a viable alternative. Quoting from that message:

https://docs.python.org/3/library/runpy.html#runpy.run_path

import runpy
file_globals = runpy.run_path("file.py")

There are subtle differences to execfile:

  • run_path always creates a new namespace. It executes the code as a module, so there is no difference between globals and locals (which is why there is only a init_globals argument). The globals are returned.

    execfile executed in the current namespace or the given namespace. The semantics of locals and globals, if given, were similar to locals and globals inside a class definition.

  • run_path can not only execute files, but also eggs and directories (refer to its documentation for details).

Answered By: Jonas Schäfer

Answer #5:

This one is better, since it takes the globals and locals from the caller:

import sys
def execfile(filename, globals=None, locals=None):
    if globals is None:
        globals = sys._getframe(1).f_globals
    if locals is None:
        locals = sys._getframe(1).f_locals
    with open(filename, "r") as fh:
        exec(fh.read()+"n", globals, locals)
Answered By: Noam

Answer #6:

You could write your own function:

def xfile(afile, globalz=None, localz=None):
    with open(afile, "r") as fh:
        exec(fh.read(), globalz, localz)

If you really needed to…

Answered By: Evan Fosmark

Answer #7:

If the script you want to load is in the same directory than the one you run, maybe “import” will do the job ?

If you need to dynamically import code the built-in function __ import__ and the module imp are worth looking at.

>>> import sys
>>> sys.path = ['/path/to/script'] + sys.path
>>> __import__('test')
<module 'test' from '/path/to/script/test.pyc'>
>>> __import__('test').run()
'Hello world!'

test.py:

def run():
        return "Hello world!"

If you’re using Python 3.1 or later, you should also take a look at importlib.

Answered By: ascobol

Answer #8:

Here’s what I had (file is already assigned to the path to the file with the source code in both examples):

execfile(file)

Here’s what I replaced it with:

exec(compile(open(file).read(), file, 'exec'))

My favorite part: the second version works just fine in both Python 2 and 3, meaning it’s not necessary to add in version dependent logic.

Answered By: ArtOfWarfare

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