Writing Pythonic Code

Code is often described as “Pythonic” or “not Pythonic” (with the implication that “Pythonic” is better.) The description is often applied to refer to code that reflects best practices which have emerged from the Python community and have become almost second nature to experienced programmers.

Reading lots of Python code (particularly from well-respected long maintained community projects) is the best way to develop this sense, but some principles are described here.

Good coding practice

Familiarity with modern coding practices that apply across most languages is a good start:

  • Compact but descriptive names for variables, functions, etc.

  • Succinct comments where necessary

  • Encapsulation of data and abstraction through functions and classes

  • Use of existing libraries rather than reimplementing

Using language features

Where Python or its standard library provides a means of accomplishing a task, it is generally preferred to use that means rather than reimplementing the wheel. The canonical example is using list comprehensions rather than for loops to transform a list:

>>> newlist = [i + 1 for i in oldlist]


>>> newlist = []
>>> for i in range(len(oldlist)):
...     newlist.append(oldlist[i] + 1)

Note there are several non-Pythonic ways to perform this task.

For those not familiar with the features of the lanaguage and the standard library, this does represent a barrier to entry. However once that knowledge is built, using the features of the language makes one’s intention much more clear. It often also results in shorter code that is easier to comprehend.

See several examples in SpacePy Python Programming Tips.

Idiom and communication

Because “code is more often read than written,” anything that improves clarity is beneficial. A list comprehension and a for loop may have the same result, but the use of a list comprehension immediately makes it apparent to the reader that the code is intended to create a new list based on some element-by-element translation of the input list. It is a pattern with a common solution, and sticking to the common solution helps make the pattern apparent so the reader of the code understands the underlying problem.

Generally this choice of the common way is referred to as “idiomatic Python.” This can be expanded to conventions such as the use of “self” as the first argument in instance methods, even though such choice is generally free.

Further Reading

A web search for “pythonic” will give a wealth of opinions. These references are a good starting point.



Doc generation date

Apr 27, 2022