Sort from a certain position in a String

Question

Take a collection of these kinds of strings:

"foo: a message"
"bar: d message"
"bar: b message"
"foo: c message"

The two strings foo: and bar: are of the same length so I would like to start sorting from index of position 5 So my output would be...

"foo: a message"
"bar: b message"
"foo: c message"
"bar: d message"

Martijn Pieters · Accepted Answer · 2014-09-19 11:02:09Z

7

Use a key function to slice each string; sorting then takes place using the values produced by the key.

sorted(inputlist, key=lambda s: s[5:])

Demo:

>>> inputlist = ['foo: a message', 'bar: d message', 'bar: b message', 'foo: c message']
>>> sorted(inputlist, key=lambda s: s[5:])
['foo: a message', 'bar: b message', 'foo: c message', 'bar: d message']

Quoting the sorted() documentation:

key specifies a function of one argument that is used to extract a comparison key from each list element: key=str.lower. The default value is None (compare the elements directly).

edited Sep 19, 2014 at 11:02

answered Sep 19, 2014 at 9:40

Martijn Pieters

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2 Comments

Ogen Over a year ago

What exactly is key referring to? Is it some sort of keyword?

BioGeek Over a year ago

@Ogen key is an optional argument. From the docs: "The optional arguments cmp, key, and reverse have the same meaning as those for the list.sort() method (described in section Mutable Sequence Types). [...] key specifies a function of one argument that is used to extract a comparison key from each list element: key=str.lower. The default value is None (compare the elements directly)."

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