[Python-Dev] PEP-xxx: Unification of for statement and list-comp syntax (original) (raw)

Greg Ewing greg.ewing at canterbury.ac.nz
Mon May 22 08:44:47 CEST 2006

Heiko Wundram wrote:

Am Montag 22 Mai 2006 01:59 schrieb Josiah Carlson: > Not everyone finds list comprehensions easy to read.

Why has Python added list-comprehensions, then? (or at least, why has Python added the 'if'-expression to list-comprehensions if they're hard to read?

LCs are useful because they're expressions rather than statements. Being expressions, they need if-clauses in order to be able to conditionally include items in the list. LCs with if-clauses don't have to be hard to read; you just need to lay them out on separate lines, as you would do when writing nested statements.

With a for-statement, there is no need for if-clauses, since you can use a nested if-statement to get the same effect. The only possible reason for wanting an if-clause would be so that you can write it on the same line, which reduces readability for no corresponding benefit.

-- Greg

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