Python: Read/Write to File

By Xah Lee. Date: . Last updated: .

To open a file and write to file do:

f=open('xfile.txt','w')

This creates a file “object”.

The second argument of “open” can be 'w' for write (overwrite exsiting file), 'a' for append, 'r' for read only.

To actually print to or read from file, use the file object's methods.

Read entire file:

text = f.read()

Read one line at a time:

line = f.readline()

Read entire file as a list of lines:

mylist = f.readlines()

To write to file, do:

f.write('yay, first line!\n')

When you are done, close the file:

f.close()

Closing files saves memory while the program is still running. You should always do that.

Here is a complete example of reading in a file and writing it to another file.

# -*- coding: utf-8 -*-
# python

f1 = open("/Users/john/in.txt","r")
f2 = open("/Users/john/out.txt","w")

for xx in f1:
    f2.write(xx)

f1.close()
f2.close()

Using 「with」 to Open File

Alternatively, you can use with:

# -*- coding: utf-8 -*-
# python

# example of opening file, using 「with」

with open("/home/jane/my_file.html", "r") as f:
    for x in f:
        print x

When using with, you do not need to close the file. Python will close any file opened within it, when the with block is done.

7. Compound statements — Python v2.7.6 documentation#with

thank to KurtSchwehr for showing me “with”.

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