IPython Notebook Magic Functions with environment variables

Question

Can I use an environment variable with a magicfunction such as writefile in my ipthon notebook?

%env WORKING_DIR=/my/path/to/my/file
!echo $WORKING_DIR

/my/path/to/my/file

but

%%writefile $WORKING_DIR/myfile.txt
sometext

IOError: [Errno 2] No such file or directory: '$WORKING_DIR/myfile.txt'

Just M · Accepted Answer · 2015-06-24 08:39:37Z

6

%%writefile $WORKING_DIR/myfile.txt does expansion of Python variable. so you need to have a WORKING_DIR python variable for this to work. $FOO works as env variable only if you are using a magics that shells out, and that get a raw $WORKING_DIR string. In which case the shell does the variable expansion.

It is possible but convoluted to do what you want, se example below:

In [1]: foo = 'a.py'

In [2]: %%writefile $foo
   ...: hi
   ...:
Writing a.py

In [3]: %env BAR=b.py
env: BAR=b.py

In [4]: import os

In [5]: %%writefile {os.environ['BAR']}
   ...: this is bar
   ...:
Writing b.py

answered Jun 24, 2015 at 8:39

Just M

28k6 gold badges85 silver badges75 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

jwillis0720 Over a year ago

That's what I thought, but couldn't figure out the "{}" wrap. Thank you

Just M Over a year ago

{smth} and $smth are the same except $smth only work on smth in [a-zA-Z0-9_] IIRC

Collectives™ on Stack Overflow

IPython Notebook Magic Functions with environment variables

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related