SSWIDL/SunPy Cheat Sheet

SolarSoft (SSWIDL) is a popular IDL software library for solar data analysis, and in fact, many parts of SunPy are inspired by data structures and functions in SSWIDL. Though IDL and Python are very different it sometimes helps to consider how to translate simple tasks between the two languages. The primary packages which provide much of the functionality for scientific data analysis in Python are NumPy and SciPy. In the following we assume that those packages are available to you and that you are imported Numpy is imported as np with the following import statement:

import numpy as np
import scipy as sp

In the following examples, a and b could be arrays. For python the arrays must be numpy arrays which can be created simply through:


where a is a python list of numbers.

Relational Operators

IDL Python
a EQ b a == b
a LT b a < b
a GT b a > b
a GE b a >= b
a LE b a <= b
a NE b a != b

Logical Operators

IDL Python
a and b a and b
a or b a or b

Math Functions

IDL Python
cos(a) np.cos(a)
alog(a) np.log(a)
alog10(a) np.alog(a)
exp(a) np.exp(a)

Math Constants

IDL Python
!pi np.pi
exp(1) np.e

Arrays Sequences

IDL Python
indgen(10) np.arange(0,10)
findgen(10) np.arange(0,10,dtype=np.float)

Array Creation

IDL Python
dblarr(3,5) np.zeros((3,5))
intarr(3,5) np.zeros((3,5),
dblarr(3,5)+1 np.ones((3,5))
intarr(3,5)+9 np.zeros((3,5), + 9
boolarr(10) np.zeros(10,dtype=bool)
identity(3) np.identity(3)

Many more examples can be found on this page