Print to an empty file in python 3

Question

can someone tell me why in python 3.4.2 when I try

import codecs
f = codecs.open('/home/filename', 'w', 'utf-8') 
print ('something', file = f)

it gives me an empty file?

Previously it was working well, but only suddenly it stopped printing to file

file= needs to be a file object. How do you create that file object? — Simeon Visser
– Simeon Visser, Commented Mar 1, 2015 at 0:01
We cannot tell you why because you need to show us a) how you are opening the file, b) how you are closing or otherwise flushing the buffers of the file and c) how you are checking that the file is empty. — Martijn Pieters
– Martijn Pieters, Commented Mar 1, 2015 at 0:03
Why are you using codecs.open() when the built-in open() function works far better? — Martijn Pieters
– Martijn Pieters, Commented Mar 1, 2015 at 0:14

Martijn Pieters · Accepted Answer · 2015-03-01 00:11:41Z

File writing is buffered to avoid hitting the performance drain that is writing to a disk. Flushing the buffer takes place when you reach a threshold, flush explicitly or close the file.

You have not closed the file, did not flush the buffer, and haven't written enough to the file to auto-flush the buffer.

Do one of the following:

Flush the buffer:
```
f.flush()
```
This can be done with the flush argument to print() as well:
```
print('something', file=f, flush=True)
```
but the argument requires Python 3.3 or newer.
Close the file:
```
f.close()
```
or use the file as a context manager (using the with stamement):
```
with open('/home/filename', 'w', encoding='utf-8') as f:
     print('something', file=f)
```
and the file will be closed automatically when the block is exited (on completion, or an exception).
Write more data to the file; how much depends on the buffering configuration.

Collectives™ on Stack Overflow

Print to an empty file in python 3

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related