The difference between exec and eval in Python

Exec can execute dynamic Python code, like the Eval function of JavaScript;

The eval function in Python calculates the Python expression and returns the result;

(Exec does not return results, print (eval ("...") prints none);

For example:

exec ("print (\" Hello, world\ ")") Hello, World exec ("a = 2")>>> a2

There is a scope (namespace, scope) concept, in order to not break the current scope, you can create a new scope (a dictionary) exec (JavaScript does not have this feature):

>>> scope = {}exec("a = 4", scope)>>> A 2>>> scope['a']4>>> scope.keys () Dict_keys ([  'a'__builtins__'])

__builtins__ contains all of the built-in functions and values

The difference between exec and eval in Python