[Python-Dev] Python 3.0rc2: problem with exec()ing files
jukka.aho at iki.fi
Tue Nov 11 13:00:36 CET 2008
The current Py3k documentation  states that the built-in exec()
function should be able to execute code from "open file objects":
--- 8< ---
exec(object[, globals[, locals]])
This function supports dynamic execution of Python code. object must be
either a string, an open file object, or a code object. [...] If it is
an open file, the file is parsed until EOF and executed.
--- 8< ---
However, at least on Python 3.0rc2 , this does not seem to work.
Please consider the following example:
1) First, let's prepare a source file which will contain a single line
of Python code (it is assumed here that it is safe to save the file in
the current working path):
>>> f = open("exectest.py", mode="wt", encoding="utf-8")
>>> f.write("print('Hello world!')\n")
2) Then, try executing that newly created file with the exec() function.
What I get is this:
>>> f = open("exectest.py", mode="rb")
Traceback (most recent call last):
File "<pyshell#30>", line 1, in <module>
TypeError: exec() arg 1 must be a string, bytes or code object
<io.BufferedReader object at 0x013832D0>
* * *
So, am I seeing this behavior because...
a) I've misinterpreted the available documentation
b) The documentation does not agree with the current development goals
c) It is a bug or a yet-to-be-implemented feature of the built-in exec()
 Python 3.0rc2 (r30rc2:67141, Nov 7 2008, 11:43:46) [MSC v.1500 32
bit (Intel)] on win32, to be exact.
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