使用for循环变量调用预定义变量

# 预定义变量列表
variables = {
    'var1': 10,
    'var2': 20,
    'var3': 30
}

# 使用for循环遍历并调用预定义变量
for key in variables:
    print(f"The value of {key} is {variables[key]}")

for key in variables:
    print(f"The value of {key} is {variables['var4']}")  # 'var4'不存在

for key in variables:
    if key in variables:
        print(f"The value of {key} is {variables[key]}")

for key in variables:
    result = variables[key] + "10"  # 尝试将整数与字符串相加

for key in variables:
    if isinstance(variables[key], int):
        result = variables[key] + 10
        print(f"The result of {key} + 10 is {result}")