Python exec in function scope cannot set value

Question

import re


value = eval("'Hello「World」'")
c = [
    "g = re.search('.*「(.*)」', value, re.IGNORECASE)",
    "print(value)",
    "value = g.group(1)",
    "print(value)"
]
if c is not None:
    for d in c:
        exec(d)


def test():
    value2 = eval("'Hello「World」'")
    c2 = [
        "g2 = re.search('.*「(.*)」', value2, re.IGNORECASE)",
        "print(value2)",
        "value2 = g2.group(1)",
        "print(value2)"
    ]
    if c2 is not None:
        for d2 in c2:
            exec(d2)

test()

Expect result:

Hello「World」
World
Hello「World」
World

Actual result:

Hello「World」
World
Hello「World」
Hello「World」

I am running in Python 3.6.2. My question is why cannot exec set the value when it is inside the function?

However, it can set on a new variable.

def test2():
    value2 = eval("'Hello「World」'")
    c2 = [
        "g2 = re.search('.*「(.*)」', value2, re.IGNORECASE)",
        "print(value2)",
        "value3 = g2.group(1)",
        "print(value3)"
    ]
    if c2 is not None:
        for d2 in c2:
            exec(d2)

test2()

Result:

Hello「World」
World
Hello「World」
World

How can I make test() change value2 inside exec?

You cannot using `exec` because `exec` always returns `None`, and inside a function, those variables are *local*, and `locals()` cannot be modified dynamically. — juanpa.arrivillaga, Jan 24 '18 at 08:43
But what are you trying to accomplish here? why do it this way? — juanpa.arrivillaga, Jan 24 '18 at 08:45
@juanpa.arrivillaga Then, how can `exec` read local variable? If it can read, why can't it write? Is there a way to pass current function context to it? — Joshua, Jan 24 '18 at 08:45
@juanpa.arrivillaga I am writing a web scraper which have site specific code that I load from config file when I execute it. — Joshua, Jan 24 '18 at 08:46
Why in the world would you do that? Why don't you make the code a function, and then call the function? — juanpa.arrivillaga, Jan 24 '18 at 08:47
But read the [docs](https://docs.python.org/3/library/functions.html#exec) particularly, the second note. — juanpa.arrivillaga, Jan 24 '18 at 08:47
@juanpa.arrivillaga Because the config is keep in another projects. Those projects hold the config. — Joshua, Jan 24 '18 at 08:48

Python exec in function scope cannot set value

0 Answers0