python之python中的返回语句

我尝试编写一个程序，但遇到了 return 语句的问题。

以下代码行引发了一条错误消息，指出变量 names 未定义。

但是，我确实使用 return 语句返回 names 并将其传递给 main 函数:

def main(names): 
    names_in() 
    print(names) 
 
# import the record, put it into a list,  pass that list to main(). 
def names_in(): 
    infile = open('names.txt','r') 
    names = infile.readlines() 
 
    infile.close() 
 
    index = 0 
    while index < len(names): 
        names[index] = names[index].rstrip('\n') 
        index += 1 
    return names 
 
main(names) 

我之前写过另一个程序做同样的事情并且一切正常，所以我不确定这里出了什么问题？

请您参考如下方法:

你的问题在这里:

main(names) 

您正在使用尚 undefined variable 名称调用您的 main 函数。您收到的错误应该显示指向此行的行号:这将验证这是问题所在。

# 'names' is not defined in this scope 
def main(names): 
    # Some code 
    # 'names' is a variable that is 'in scope' here because it's passed as an 'argument' 
 
# 'names' is not defined in this scope either 
 
# import the record, put it into a list,  pass that list to main(). 
def names_in(): 
    infile = open('names.txt','r') 
    names = infile.readlines()  # defines 'names' for this scope 
 
    # more code 
    return names  # because 'names' is defined it can return it 
 
# 'names' is no longer defined in this scope 
main(names)  # This fails because when the compiler tries to resolve 'names' it can't find anything 

根据您显然正在尝试做的事情，您需要像这样修改您的 main 函数:

def main(): 
    print(names_in()) 

然后这样调用它:

main() 

另外请注意，您似乎对代码的执行方式有些困惑。如果我写:

def a(): 
    print("a") 
 
def b(): 
    print("b") 
 
print("c") 
b() 
a() 

它被翻译成等同于:

print("c") 
print("b") 
print("a") 

def 语句被有效地复制粘贴到它们被调用的地方。