How do you append to a file in Python?
with open("test.txt", "a") as myfile: myfile.write("appended text")
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You need to open the file in append mode, by setting "a" or "ab" as the mode. See open().
When you open with "a" mode, the write position will always be at the end of the file (an append). You can open with "a+" to allow reading, seek backwards and read (but all writes will still be at the end of the file!).
>>> with open('test1','wb') as f: f.write('test') >>> with open('test1','ab') as f: f.write('koko') >>> with open('test1','rb') as f: f.read() 'testkoko'
Note: Using 'a' is not the same as opening with 'w' and seeking to the end of the file - consider what might happen if another program opened the file and started writing between the seek and the write. On some operating systems, opening the file with 'a' guarantees that all your following writes will be appended atomically to the end of the file (even as the file grows by other writes).
A few more details about how the "a" mode operates (tested on Linux only). Even if you seek back, every write will append to the end of the file:
>>> f = open('test','a+') # Not using 'with' just to simplify the example REPL session >>> f.write('hi') >>> f.seek(0) >>> f.read() 'hi' >>> f.seek(0) >>> f.write('bye') # Will still append despite the seek(0)! >>> f.seek(0) >>> f.read() 'hibye'
In fact, the
fopen manpage states:
Opening a file in append mode (a as the first character of mode) causes all subsequent write operations to this stream to occur at end-of-file, as if preceded the call:
fseek(stream, 0, SEEK_END);
Old simplified answer (not using
Example: (in a real program use
with to close the file - see the documentation)
>>> open("test","wb").write("test") >>> open("test","a+b").write("koko") >>> open("test","rb").read() 'testkoko'
I always do this,
f = open('filename.txt', 'a') f.write("stuff") f.close()
It's simple, but very useful.
Python has many variations off of the main three modes, these three modes are:
'w' write text 'r' read text 'a' append text
So to append to a file it's as easy as:
f = open('filename.txt', 'a') f.write('whatever you want to write here (in append mode) here.')
Then there are the modes that just make your code fewer lines:
'r+' read + write text 'w+' read + write text 'a+' append + read text
Finally, there are the modes of reading/writing in binary format:
'rb' read binary 'wb' write binary 'ab' append binary 'rb+' read + write binary 'wb+' read + write binary 'ab+' append + read binary
when we using this line
open(filename, "a"), that
a indicates the appending the file, that means allow to insert extra data to the existing file.
You can just use this following lines to append the text in your file
def FileSave(filename,content): with open(filename, "a") as myfile: myfile.write(content) FileSave("test.txt","test1 \n") FileSave("test.txt","test2 \n")