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今天有个很可爱的人问我一个看起来很简单的奇怪现象，看代码
def print_models(unprinted_design,completed_models):
"""模拟打印每个设计，直到没有未打印的设计为止
打印每个设计后，都将其打印到列表completed_models中
"""
while unprinted_design:
current_design=unprinted_design.pop()
#模拟根据设计制作3D打印模型的过程
print("Printing model:"+current_design)
completed_models.append(current_design)
def show_completed_models(completed_models):
"""显示打印好的所有模型"""
print("\nThe following models have been printed:")
for completed_model in completed_models:
print(completed_model)
if __name__ == '__main__':
'''unprinted_designs = ['11','22','33']
completed_models = []
print_models(unprinted_designs,completed_models)
show_completed_models(completed_models)'''
unprinted_designs = ['11', '22', '33']
completed_models = []
print_models(unprinted_designs, completed_models)
show_completed_models(completed_models)别管这个是干嘛的，先看结果
Printing model:33
Printing model:22
Printing model:11
The following models have been printed:
33
22
11
Process finished with exit code 0到这里没什么，这个py我们命名为uuu
然后我新建了一个yyy.py，里面只有一行代码
from uuu import print_models as pm引入uuu里的一个函数，可是奇怪的是，运行完这个yyy之后，输出和运行uuu的一样！
Printing model:33
Printing model:22
Printing model:11
The following models have been printed:
33
22
11
Process finished with exit code 0明明我们连参数都没给啊？
这是因为，我们引入py文件的时候，被引入的py文件一定要有主函数入口
if __name__ == '__main__':就是这个东东，没有这个，引入该py文件的时候会编译该py文件所有非函数的代码，而事实上我们一般只需要调用其中的函数即可，上面这个例子，没有主函数的时候，底下调用参数运行函数的代码也被执行了，所以会有和uuu一样的输出。
那么应该怎么做呢
def print_models(unprinted_design,completed_models):
"""模拟打印每个设计，直到没有未打印的设计为止
打印每个设计后，都将其打印到列表completed_models中
"""
while unprinted_design:
current_design=unprinted_design.pop()
#模拟根据设计制作3D打印模型的过程
print("Printing model:"+current_design)
completed_models.append(current_design)
def show_completed_models(completed_models):
"""显示打印好的所有模型"""
print("\nThe following models have been printed:")
for completed_model in completed_models:
print(completed_model)
if __name__ == '__main__':
unprinted_designs = ['11','22','33']
completed_models = []
print_models(unprinted_designs,completed_models)
show_completed_models(completed_models)
'''unprinted_designs = ['11', '22', '33']
completed_models = []
print_models(unprinted_designs, completed_models)
show_completed_models(completed_models)'''输出结果如下：
Process finished with exit code 0是不会有输出的
这个例子告诉我们，女生是不讲道理的生物，自己领悟吧。