safish_eval.py

import ast

def get_safe_function(code):
    expression = ast.parse(code).body[0]
    if expression.value.__class__.__name__ == 'Lambda':
        return eval(code)
 
    else:
        logger.warning("Got an unsafe code: %s", repr(code))

    return lambda x: x


exec1 = get_safe function('lambda x: x.strip()')
exec2 = get_safe function('__import__("os").system("rm -rf /")')

assert exec1("  aaa    ") == "aaa"
assert exec2("  aaa    ") == "  aaa    "