如何在 python 的变量中使用代码？

Question

I tried with exec() but it doesn't work for what i'm trying to do:

math = "1 + 1"
a = exec(math)
print(a)

when "a" is printed i get

None

how can i do something like this?

Answer 1

exec("a = 1 + 1")
print(a)

2

b = eval("1 + 1")
print(b)

2

You're getting None because exec always returns None , instead it execute the expression. What you might want is eval , it returns whatever is evaluated inside.

Notice that both of them are quite dangerous as malicious programs can easily assess your data by input.

Why is using 'eval' a bad practice?