CODEWITHSUNDEEP
pythonipythonipython-magic
nadapez
nadapez

Reputation: 2707

How to pass a variable to magic ´run´ function in IPython

I want to do something like the following:

In[1]: name = 'long_name_to_type_every_now_and_then.py'

In[2]: %run name

but this actually tries to run 'name.py', which is not what I want to do.

Is there a general way to turn variables into strings?

Something like the following:

In[3]: %run %name%

Upvotes: 102

Views: 51489

Answers (6)

dsz
dsz

Reputation: 5202

More generally, but lacking pretty formatting:

ipy = get_ipython()
ipy.run_cell_magic("spark", "", f"""
from_dt = "{start_date}"
to_dt = "{end_date}"
""")

effectively runs under a %%spark magic. For single % line magic:

ipy = get_ipython()
ipy.run_line_magic("sql", "", f"SELECT * FROM {table_name}")

Upvotes: 0

Philippe Hebert
Philippe Hebert

Reputation: 2028

If by 'variable' you mean a variable available in the user namespace, then I'd suggest to use get_ipython().ev(varname) (docs) to get your variable in your function:

from __future__ import print_function
import argparse
import shlex

from IPython import get_ipython
from IPython.core.magic import register_cell_magic

@register_cell_magic
def magical(line, cell):
    parser = argparse.ArgumentParser()
    parser.add_argument("varname")
    # using shlex to split the line in a sys.argv-like format
    args = parser.parse_args(shlex.split(line))
    ipython = get_ipython()

    v = ipython.ev(args.varname)
    # do whatever you want here
    print(v)

This template above served me well - I used it to make a jinja2 cell magic that also prints to file whenever the cell is run.

Upvotes: 1

Barış Deniz Sağlam
Barış Deniz Sağlam

Reputation: 131

In case there might be space in argument, e.g. filename, it is better to use this:

%run "$filename"

Upvotes: 4

Emmett Butler
Emmett Butler

Reputation: 6207

It seems this is impossible with the built-in %run magic function. Your question led me down a rabbit hole, though, and I wanted to see how easy it would be to do something similar. At the end, it seems somewhat pointless to go to all this effort to create another magic function that just uses execfile(). Maybe this will be of some use to someone, somewhere.

# custom_magics.py
from IPython.core.magic import register_line_magic, magics_class, line_magic, Magics

@magics_class
class StatefulMagics(Magics):
    def __init__(self, shell, data):
        super(StatefulMagics, self).__init__(shell)
        self.namespace = data

    @line_magic
    def my_run(self, line):
        if line[0] != "%":
            return "Not a variable in namespace"
        else:
            filename = self.namespace[line[1:]].split('.')[0]
            filename += ".py"
            execfile(filename)
        return line

class Macro(object):
    def __init__(self, name, value):
        self.name = name
        self._value = value
        ip = get_ipython()
        magics = StatefulMagics(ip, {name: value})
        ip.register_magics(magics)

    def value(self):
        return self._value

    def __repr__(self):
        return self.name

Using this pair of classes, (and given a python script tester.py) it's possible to create and use a "macro" variable with the newly created "my_run" magic function like so:

In [1]: from custom_magics import Macro

In [2]: Macro("somename", "tester.py")
Out[2]: somename

In [3]: %my_run %somename
I'm the test file and I'm running!
Out[3]: u'%somename'

Yes, this is a huge and probably wasteful hack. In that vein, I wonder if there's a way to have the name bound to the Macro object be used as the macro's actual name. Will look into that.

Upvotes: 1

David Wolever
David Wolever

Reputation: 154494

Use get_ipython() to get a reference to the current InteractiveShell, then call the magic() method:

In [1]: ipy = get_ipython()

In [2]: ipy.magic("run foo.py")
ERROR: File `u'foo.py'` not found.

Edit See minrk's answer — that's a much better way to do it.

Upvotes: 14

minrk
minrk

Reputation: 38598

IPython expands variables with $name, bash-style. This is true for all magics, not just %run.

So you would do:

In [1]: filename = "myscript.py"

In [2]: %run $filename
['myscript.py']

myscript.py contains:

import sys
print(sys.argv)

Via Python's fancy string formatting, you can even put expressions inside {}:

In [3]: args = ["arg1", "arg2"]

In [4]: %run $filename {args[0]} {args[1][-2:]}
['myscript.py', 'arg1', 'g2']

Upvotes: 167

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