我应该在函数外部还是内部打开文件？

Question

Maybe this question makes no sense, but I was wondering if there was a "recommended practice" on how to pass a file to a function in Python.

Should I pass the file's path or the opened file itself ?

Should I do :

def func(file):
  file.write(...)

with open(file_path, 'w') as file:
  func(file)

...or :

def func(file_path):
  with open(file_path, 'w') as file:
    file.write(...)

func(file_path)

?

Is there some reason to use one method instead of the other ?

Answer 1

Both ways have their advantages and disadvantaged. When a function takes an open file object, it becomes easier to use with other file-like object such s io.StringIO . On the other hand, using a with statement inside a function is very elegant. A hybrid solution would be accepting both a path (string) and a file-like object. Several libraries do that.

Answer 2

Passing a file like object is recommended over passing a path. This means it will be easier to reuse your function with other types of files not just ones with a path on disk, such as BytesIO https://docs.python.org/3/library/io.html#io.BytesIO .

You can still use the with statement on the file like object, you don't have to use it only when you open it.