python - 将输入存储为函数中的变量，然后在另一个函数中调用该变量

Question

我正在学习 Python 3，但在编写程序时遇到了困难。

我正在尝试编写一些代码来读取文件，然后打印出其文本片段。这是我到目前为止所拥有的。

def greeting():
    """Print a message when the program starts."""
    greeting = "Welcome to the file reader."
    greeting += "\nEnter the name of the file you would like to read. "
    greeting += "If the file is in a different folder, type the file path."
    greeting += "\n(Type 'exit' to quit, or 'help' for help.) "
    file_name = input(greeting)


def read_file():
    """Search for the file, then read it line by line. Print an error if the file isn't found."""
    try:
        with open(file_name) as f_obj:
            file_contents = f_obj.readlines()
            print(file_name + " was opened successfully")
    except FileNotFoundError:
        print("Error: File not found.")


greeting()
read_file()
print(file_contents[:9])

当我运行此代码时，我输入一个文件名(同一目录中的文本文件)，然后收到此错误。

Traceback (most recent call last):
  File "reader.py", line 21, in <module>
    read_file()
  File "reader.py", line 13, in read_file
    with open(file_name) as f_obj:
NameError: name 'file_name' is not defined

所以我的问题是，如何正确地将用户输入存储在函数中，然后在另一个函数中调用它？

Answer 1

您想要做的不是将输入存储在函数的本地范围内(这是违反直觉的)，因为您需要其他地方的数据(其他函数)。

您应该从 greeting() 函数返回数据，以便可以在其他逻辑中使用它，如下所示:

def greeting():
    """Print a message when the program starts."""
    greeting = "Welcome to the file reader."
    greeting += "\nEnter the name of the file you would like to read. "
    greeting += "If the file is in a different folder, type the file path."
    greeting += "\n(Type 'exit' to quit, or 'help' for help.) "
    file_name = input(greeting)
    return file_name  # Return user input


def read_file(file_name):
    """Search for the file, then read it line by line. Print an error if the file isn't found."""
    try:
        with open(file_name) as f_obj:
            file_contents = f_obj.readlines()
            print(file_name + " was opened successfully")
            return file_contents  # Return the contents of the file
    except FileNotFoundError:
        print("Error: File not found.")


input_file_name = greeting()
output_file_contents = read_file(input_file_name)
print(output_file_contents[:9])

注意:如果找不到该文件，此代码将会出现问题。它将到达脚本中的最后一个 print 行并失败，因为如果文件不存在，则前一个函数调用没有输出。