python eval()中的有效语句是什么? [英] What are valid statements inside a python eval()?

问题描述

我尝试过

eval('print("hello world")')
eval('return 0')

这两个都不正确.为什么它们无效?使用eval()时应遵循哪些规则(尽可能少使用)?

which are both incorrect. Why are they invalid and what rules should I follow when using eval() (other than as little as possible)?

推荐答案

在Python中，eval()评估表达式(会产生值的东西). print和return都定义为语句(但是在Python 3中，print实际上是一个函数调用，它是一个表达式).对于执行语句，您需要使用 exec声明.

In Python, eval() evaluates expressions (something that results in a value). Both print and return are defined as statements (however in Python 3, print is actually a function call, which is an expression). In the case of executing statements, you need to use the exec statement instead.

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