what does '%%file test.py' mean in python?

Question

Just as the title said. I'm trying to figure out what does the '%%' mean. It seems to be not a Placeholder here?

%%file test_theano.py
from theano import config
print 'using device:', config.device

%%file is an alias for the %%writefile cell magic in ipython, which writes the contents of this cell to the file specified. See: ipython.org/ipython-doc/3/interactive/magics.html — Craig
– Craig, Commented Apr 2, 2017 at 3:46

Community · Accepted Answer · 2017-05-23 12:25:51Z

12

That %%file command is not Python, but rather an IPython "magic" command. It puts the content which follows into a file named by its parameter.

Some time ago it was renamed %%writefile, but the old name is still supported, though no longer documented. You can find the documentation for %%writefile here: https://ipython.org/ipython-doc/3/interactive/magics.html

If you try it in an IPython shell it will be quite clear what it does - it creates a file called test_theano.py in the current directory.

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answered Apr 2, 2017 at 3:27

John Zwinck

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Thanks @John Zwinck you are correct about it. I just realized it when I try it in an IPython notebook and get a file named test_theano.py.

maleckicoa · Accepted Answer · 2020-02-03 21:38:37Z

1

Just to give an example to support what John wrote.

Run this in Ipython (or some Ipython shell such as Jupyter):

%%file test.py

some_list=[1,2,3]

The program will return

Writing test.py

IPython created a test.py file in the imediate environment. Open the test.py and you would see:

 some_list=[1,2,3]

answered Feb 3, 2020 at 21:38

maleckicoa

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