Python中NameError的变量未定义问题的原因及解决方案

print(unknown_variable)  # NameError: name 'unknown_variable' is not defined

def func():
    print(global_var)  # NameError: name 'global_var' is not defined

global_var = 10
func()

my_var = 10
print(my_var)  # 正确输出：10
print(my_varr)  # NameError: name 'my_varr' is not defined

print(math.sqrt(16))  # NameError: name 'math' is not defined

try:
    print(unknown_variable)
except NameError as e:
    print(f"发生NameError: {e}")
    print("请检查变量是否定义或拼写是否正确。")

def func():
    print(globals())  # 打印全局变量字典
    print(locals())   # 打印局部变量字典

func()

# 定义变量
my_var = 10
print(my_var)  # 正确输出：10

global_var = 10

def func():
    global global_var  # 声明为全局变量
    print(global_var)  # 正确输出：10

func()

my_var = 10
print(my_var)  # 正确输出：10
# print(my_varr)  # 拼写错误，已被注释掉

import math  # 导入math模块
print(math.sqrt(16))  # 正确输出：4.0

def isdefined(var_name):
    try:
        eval(var_name)
        return True
    except NameError:
        return False

my_var = 10
print(isdefined("my_var"))  # 输出：True
print(isdefined("unknown_var"))  # 输出：False