Installation

To begin, we install pIDLy:

pip install pidly

Then we install idlmagic:

In [ ]:
%install_ext https://raw.github.com/ebellm/ipython-idlmagic/master/idlmagic.py

Usage

When starting a new notebook, we load the magic:

In [1]:
%load_ext idlmagic
IDL not found, using GDL

(I am using GDL rather than IDL on this computer. idlmagic will first look for the idl interpreter on the search path and and fall back to gdl if needed.)

Line magics

The %idl magic enables one-line execution of IDL commands in the IPython interpreter or notebook:

In [2]:
%idl print, findgen(5)
      0.00000      1.00000      2.00000      3.00000      4.00000

Cell magics

Multi-line input can be entered with the %%idl cell magic:

In [3]:
%%idl
x = findgen(5)
y = x^2.
; comments are supported
print, $ ; as are line continuations
mean(y)
% Compiled module: MEAN.
      6.00000

Passing variables between Python and IDL

The mechanisms for passing variables to and from IDL are based on those in the built-in %R and %octave magics.

Variables may be pushed from Python into IDL with %idl_push:

In [4]:
msg = '  padded   string   '
import numpy as np
arr = np.arange(5)
In [5]:
%idl_push msg arr
In [6]:
%%idl
print, strcompress(msg,/REMOVE_ALL)
print, reverse(arr)
paddedstring
                     4                     3                     2
                     1                     0

Similarly, variables can be pulled from IDL back to Python with %idl_pull:

In [7]:
%idl arr += 1
In [8]:
%idl_pull arr
In [9]:
arr
Out[9]:
array([1, 2, 3, 4, 5])

Variables can also be pushed and pulled from IDL inline using the -i (or --input) and -o (or --output) flags:

In [10]:
Z = np.array([1, 4, 5, 10])
In [11]:
%idl -i Z -o W W = sqrt(Z)
In [12]:
W
Out[12]:
array([ 0.99999994,  1.99999988,  2.23606801,  3.1622777 ], dtype=float32)

Plotting

Inline plots are displayed automatically by the IPython notebook. IDL Direct graphics are used. The optional -s width,height argument (or --size; default: 600,375) specifies the size of the resulting png image.

In [13]:
%%idl -s 400,400
plot,findgen(10),xtitle='X',ytitle='Y'
% Compiled module: WRITE_PNG.

Known issues and limitations

  • Only one plot can be rendered per cell
  • Processing for possibly unused plot output slows execution
  • Scalar variables from IDL may be returned as single-element Numpy arrays
  • The %idl line magic fails with TypeError: coercing to Unicode: need string or buffer, dict found in IPython 0.13.2 and below due to a known bug; IPython 1.0 and later should work as expected.