How to fix the syntax of a function which is in string format?

Question

I have a text file containing python functions in string format. My code reads each function from the text file, feeds it with the appropriate inputs and then runs it. To run a function string (for example fun_str) from the text file, I use the following snippet in my code:

dict = {}
exec(fun_str, globals(), dict)
f, = dict.values()
f()

As long as each function string has the python standard syntax (in terms of indentations, new lines, etc), the code works well. However, if the code reads a function string such as:

"def fun(list): output_list = [] for i in list: if i not in output_list: output_list.append(i) return output_list"

(all in one line)

then SyntaxError: invalid syntax is raised with ^^^ under for.

Is there any built-in module or any approach to fix the function string so that it follows the standard syntax before it is run by exec?

Asked By: Bsh

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Source

Answer 1

If you take some python code and remove all newlines, it is not necessaraily possible to convert back to the original.

For example:

def f(x): if x == None: return doSomething(x)

could mean either:

def f(x):
    if x == None:
        return doSomething(x)

or

def f(x):
    if x == None:
        return
    doSomething(x)

So it wouldn’t be possible unless you know something about that code that allows you to unambiguously convert it back to its original meaning.

Answered By: EDD

How to fix the syntax of a function which is in string format?

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