Syntax

Syntax#

This section covers common ipython features such as the ability to use ipython magic.

Embeded magics#

Note that you can embed line-based magic in Python code.

The following code stores the results of the %ls magic in the result variable.

result = %ls
print(result)

magics.ipynb

None

Python variables#

You can embed Python variables in bash expressions precending them with the $ sign. The variable’s value will then be substituted into the bash command and executed.

The following cell defines the dir_name variable and creates a folder based on the specified in the dir_name value.

dir_name = "/tmp/dir_from_variable"
!mkdir $dir_name

Next code insures that the directory specified in the dir_name really created.

!ls /tmp | grep dir_from_variable

dir_from_variable

The next cell substitutes the dir_name in order to delete the directory that was created earlier.

!rm -rf $dir_name

Omit %#

If you don’t have a corresponding name in the namespace, you can omit the % to call linebase magic.

For example the following cell applies timeit to the list generator and calls it just by name without any prefixes.

timeit [i for i in range(1000)]

23.6 µs ± 134 ns per loop (mean ± std. dev. of 7 runs, 10,000 loops each)

Note: Magics cannot be called without % if they are in the nested namespace. The following cell tries to refer to the pwd magic inside the if block, causing an error.

try:
    if True: res = pwd
except Exception as e:
    print(e)

name 'pwd' is not defined

But the same syntax, but forcing the interpreter to use magic, works fine.

if True: res = %pwd
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