Python - 'str' object has no attribute 'close'

Question

I am having a great time trying to figure out why there doesn't need to be a closing attribute for this few lines of code I wrote:

from sys import argv
from os.path import exists

script, from_file, to_file = argv

file_content = open(from_file).read()
new_file = open(to_file, 'w').write(file_content)

new_file.close()

file_content.close()

I read some things and other people's posts about this, but their scripts were a lot more complicated than what I'm currently learning, so I couldn't figure out why.

I am doing Learning Python the Hard Way and would appreciate any help.

Answer 1

file_content is a string variable, which contains contents of the file -- it has no relation to the file. The file descriptor you open with open(from_file) will be closed automatically: file sessions are closed after the file-objects exit the scope (in this case, immediately after .read()).

Answer 2

open(...) returns a reference to a file object, calling read on that reads the file returning a string object, calling write writes to it returning None, neither of which have a close attribute.

>>> help(open)
Help on built-in function open in module __builtin__:

open(...)
    open(name[, mode[, buffering]]) -> file object

    Open a file using the file() type, returns a file object.  This is the
    preferred way to open a file.

>>> a = open('a', 'w')
>>> help(a.read)
read(...)
    read([size]) -> read at most size bytes, returned as a string.

    If the size argument is negative or omitted, read until EOF is reached.
    Notice that when in non-blocking mode, less data than what was requested
    may be returned, even if no size parameter was given.
>>> help(a.write)
Help on built-in function write:

write(...)
    write(str) -> None.  Write string str to file.

    Note that due to buffering, flush() or close() may be needed before
    the file on disk reflects the data written.

Theres a couple ways of remedying this:

>>> file = open(from_file)
>>> content = file.read()
>>> file.close()

or with python >= 2.5

>>> with open(from_file) as f:
...     content = f.read()

The with will make sure the file is closed.