Problem using exec within class' function in Python

Question

The following code works as expected

name = "Test"
myname = ""
exec('myname ="' + name + '"')
print(myname)

Which shows as result:

Test

Problem

However, if I define the same within a function in a class and execute it I get as result an empty string.

class new(object):
    def __init__(self, name):
        self.print(name)

    def print(self, name):
        myname = ""
        exec('myname ="' + name + '"')
        print(myname)

a = new("My name")

The above is a toy example code of a bigger code.

Question

How to define the function so as to get the same result? The exec function is actually needed in the bigger code.

Have you read the documentation for exec? What does it say about the behavior in local scopes? Hint, look at the last note. — juanpa.arrivillaga
– juanpa.arrivillaga, Commented Dec 21, 2022 at 20:24
Why are you using exec at all? I half suspect you don't need it as much as you think you do. — chepner
– chepner, Commented Dec 21, 2022 at 20:43
In this example case it's not needed of course. But in the real case I'm working in it's needed to shorten the code. — Cedric Zoppolo
– Cedric Zoppolo, Commented Dec 22, 2022 at 13:22

Unmitigated · Accepted Answer · 2022-12-21 19:19:28Z

2

You can pass a dictionary as the globals (or locals) for exec.

def print(self, name):
    d = {"myname": ""}
    exec('myname ="' + name + '"', d)
    print(d["myname"])

answered Dec 21, 2022 at 19:19

Unmitigated

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1 Comment

Cedric Zoppolo Over a year ago

Is there no way to assign a value to a variable myname within the print function using the exec function? I tried what you proposed and it works. But I still can't create a variable named myname which gets what I want to be assigned. In particular in my bigger code I need a DataFrame get created using exec and then access one of it's columns. I may ask another question maybe...

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