What is an alternative to execfile in Python 3?

According to the documentation, instead of

execfile("./filename") 

Use

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

See:

• What’s New In Python 3.0

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:

• http://docs.python.org/release/2.7.3/library/functions.html#execfile
• http://docs.python.org/release/3.2.3/library/functions.html#compile
• http://docs.python.org/release/3.2.3/library/functions.html#exec

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().