Writing to a text file on the pyboard fails ?.

[alexsunny123]

Hello,


In this example, the expectation is that I ought to be able to read back exactly what I put into the file. What I actually get back is an empty file.

It occurred to me that this might actually be an expected behavior, and that perhaps there is a manual technique that allows me to flush the file?
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Micro Python v1.3.3 on 2014-10-02; PYBv1.0 with STM32F405RG
Type "help()" for more information.
>>> import os
>>> os.listdir()
['main.py', 'pybcdc.inf', 'README.txt', 'boot.py', '.Trash-1000']
>>> open("foo.txt", "w").write("hello world")
11
>>> os.listdir()
['main.py', 'pybcdc.inf', 'README.txt', 'boot.py', 'foo.txt', '.Trash-1000']
>>>
>>> open("foo.txt").read()

''
The use case here, is that I want to do stuff like:
* Periodically record something to a local text file, either in pyboard memory or on the SD card.
* As part of a code deployment process, automatically generate ,py files on the pyboard which can then be executed.


thanks
alexsunny

[Roberthh]

You should close the file, or use a "with ..." clause.

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f = open("foo.txt", "w")
f.write("hello world")
f.close()

or:

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with open("foo.txt", "w") as f:
    f.write("hello world")

[pythoncoder]

The "with" context manager is preferable because the file will always be closed, even if an exception occurs.

[rcolistete]

Remember to sync the buffer with the file system after closing the file. For Pyboard, it is the pyb.sync() function :

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pyb.sync()