Python: Read/Write to File
To open a file and write to file do:
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:
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
# -*- coding: utf-8 -*- # python # example of opening file, using 「with」 with open("/home/joe/my_file.html", "r") as f: for x in f: print x
with, you do not need to close the file. Python will close any file opened within it, when the
with block is done.
thank to Kurt Schwehr for showing me “with”.
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