Can you create a function that has custom code via parameters in python?

Question

What I mean by the title is this for ex:

def write_to_file(*params):
    with open(path, 'r+', encoding="utf-8") as file:
        content = file.read()
        file.seek(0) 

        # custom code via func parameters to be executed
        # for example *params will be ["file.write("test" + '\n')", "]
        # and here will be like for loop that goes through the params ?
        # for code in params:
            #code.execute() ?
    
        file.truncate()

Hopefully I explained it well, just wondering if you can do any of this.

// Edit (better explanation): I want to convert string into a code executable, "print(x)" -> print(x) that will be called in a function.

You can pass a function into another function and then call it. Is that what you need? — khelwood
– khelwood, Commented Jan 13, 2022 at 12:40
The reasonable way to do this is to have your function accept another function, i.e. a "callback" — juanpa.arrivillaga
– juanpa.arrivillaga, Commented Jan 13, 2022 at 12:41
for ex.: write_to_file(["x = 1", "print(x)", "x = len(content)", "print(x)"]) — ZippoKs
– ZippoKs, Commented Jan 13, 2022 at 12:42
Or to reverse it: only do this if you are in full control of the incoming strings, like: you typing them yourself. Otherwise, just assume your worst personal enemy sits in front of the computer and is allowed to type in those strings to be evaluated. — GhostCat
– GhostCat, Commented Jan 13, 2022 at 12:53

muliku · Accepted Answer · 2022-01-13 12:43:31Z

2

pass the function itself:

def write_to_file(func):
    with open(path, 'r+', encoding="utf-8") as file:
        content = file.read()
        file.seek(0) 
        func()
        file.truncate()

def func():
    print("foo")

write_to_file(func)

answered Jan 13, 2022 at 12:43

muliku

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4 Comments

ZippoKs Over a year ago

I didn't explain it well, my bad. I want to convert string into a code executable, "print(x)" -> print(x) in a function.

matszwecja Over a year ago

Evaluating arbitrary user-input code is a terrible idea

muliku Over a year ago

@ZippoKs in that case you van use 'eval': eval("print(1)") but that's not a good practice. If you need to use it, your code needs some reevaluation

ZippoKs Over a year ago

Yes, eval was what I'm looking for, will do more research about it, thanks guys!

Harshit Gupta · Accepted Answer · 2022-01-13 12:56:36Z

-1

If you just need to execute code from a string (reading the contents of a file with .read() also returns them in form of a single or multiline string), then you might simply use eval() function for the purpose.

eval() is a built-in Python function that can evaluate any expression given in it, and any errors in expressions are also thrown on console accordingly. This function just evaluates the given single-line expression, and does not support assignment and other related operators. For other purposes, you may also want to use exec() Python function.

I initially wanted to comment it, but I lack 2 reputation score for it at the time of posting it, so have to post it as an answer here.

edited Jan 13, 2022 at 12:56

answered Jan 13, 2022 at 12:48

Harshit Gupta

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1 Comment

ZippoKs Over a year ago

Yes, eval was what I'm looking for, will do more research about it, thanks guys!

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