I want to define a Python function using eval:
func_obj = eval('def foo(a, b): return a + b')
But it return invalid syntax error? How can I make it?
Btw, how can I transform a function obj to a string object in Python?
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1why do you need eval()?user2665694– user26656942013-11-02 13:00:05 +00:00Commented Nov 2, 2013 at 13:00
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1Does this answer your question? How do I execute a string containing Python code in Python?Georgy– Georgy2020-08-03 18:04:40 +00:00Commented Aug 3, 2020 at 18:04
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4 Answers
Use exec. eval is used for expressions not statements.
>>> exec 'def foo(a, b): return a + b'
>>> foo(1, 2)
3
Function code from function object:
def func():
""" I'm func """
return "Hello, World"
...
>>> import inspect
>>> print inspect.getsource(func)
def func():
""" I'm func """
return "Hello, World"
answered Nov 2, 2013 at 12:58
Ashwini Chaudhary
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7 Comments
xunzhang
how can I convert a function object to string?
Ashwini Chaudhary
@xunzhang It is possible only if function is defined somewhere, use
inspect.getsource.xunzhang
see this question(stackoverflow.com/questions/19740380/…), that is what I really need~
Ashwini Chaudhary
@xunzhang Please ask only one question at a time.
kd4ttc
Upvoted because it is clear with good examples, and doesn’t bother with explaining why this is a bad thing because that is all over the internet, and we should assume intelligence on the part of readers of stackoverflow.
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You can use eval with lambda, like:
func_obj = lambda a, b: eval('a + b')
answered Nov 2, 2013 at 13:25
Saullo G. P. Castro
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1 Comment
therealak12
def f(a,b) = return eval('a+b') does the same.def test_eval():
exec('def foo(a, b): return a + b')
foo(1, 2)
@niitsuma This code will return error: NameError: name 'foo' is not defined
This is because foo is defined in other scope that you execute it. To fix it and make it visible in oouter scope, you can make foo global variable:
def test_eval():
exec('global foo\ndef foo(a, b): return a + b')
foo(1, 2)
Comments
I wrote
def test_eval():
exec('def foo(a, b): return a + b')
foo(1, 2)
in mypackage/tests/test_mycode.py with approprite mypackage/setup.py.
But python setup.py test cause
NameError: name 'foo' is not defined.
How to test codes from string?
