Question

Need some help with Python syntax

Pesudo code

if param is not None in params, param replace(‘xx’, ‘x’)

I get this far:

param.replace('|', '/') for param in ("bar|one","bar|two")

My question is how to add a None check in this line of code?

Answer 1

Perhaps:

[ param.replace("|", "/") if param is not None else None for param in iterable ]

Or maybe a tiny bit more legible if we switch the logic around just a bit:

[ None if param is None else param.replace("|", "/") for param in iterable ]

I like the second version a little better because if breaks up the None else None nonsense that was present in the first one…

This differs slightly from the (initial) answer by @Tim Pietzcker. His (initial) answer will filter None values out of the input iterable whereas this answer will pass them through.

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Here we use the python conditional expression (which is sometimes known as the “ternary operator” in other languages). The syntax is:

value_if_true if conditional_expression else value_if_false