Velocity Reviews > How to sort list of String without considering Special characters andwith case insensitive

# How to sort list of String without considering Special characters andwith case insensitive

san
Guest
Posts: n/a

 11-27-2012
Please let me know how to sort the list of String in either ascending / descending order without considering special characters and case.
ex: list1=['test1_two','testOne','testTwo','test_one']
Applying the list.sort /sorted method results in sorted list ['test1_two', 'testOne', 'testTwo', 'test_one']
but the without considering the special characters and case it should be
['testOne','test_one', 'test1_two','testTwo'] OR ['test_one','testOne','testTwo', 'test1_two' ]

list.sort /sorted method sorts based on the ascii value of the characters but Please let me knwo how do i achieve my expected one

MRAB
Guest
Posts: n/a

 11-27-2012
On 2012-11-27 17:31, san wrote:
> Please let me know how to sort the list of String in either ascending / descending order without considering special characters and case.
> ex: list1=['test1_two','testOne','testTwo','test_one']
> Applying the list.sort /sorted method results in sorted list ['test1_two', 'testOne', 'testTwo', 'test_one']
> but the without considering the special characters and case it should be
> ['testOne','test_one', 'test1_two','testTwo'] OR ['test_one','testOne','testTwo', 'test1_two' ]
>
> list.sort /sorted method sorts based on the ascii value of the characters but Please let me knwo how do i achieve my expected one
>

(I'm using Python 3.)

The .sort method accepts a 'key' argument, which lets you pass a
function that transforms the value being sorted before comparison:

>>> def make_key(string):

return string.replace('_', '').upper()

>>> list1 = ['test1_two', 'testOne', 'testTwo', 'test_one']
>>> list1.sort(key=make_key)
>>> list1

['test1_two', 'testOne', 'test_one', 'testTwo']

I don't know how you define 'special'.

You could remove any characters which are special or keep any
characters which are not special, depending on how many characters are
defined as 'special':

from string import ascii_letters

# Sets are faster for this kind of thing.
ascii_letters = set(ascii_letters)

def make_key(string):
return ''.join(c for c in string if c in ascii_letters).upper()

list1 = ['test1_two', 'testOne', 'testTwo', 'test_one']
list1.sort(key=make_key)

print(list1)

# Output is: ['testOne', 'test_one', 'test1_two', 'testTwo']

Guest
Posts: n/a

 11-27-2012
san wrote:

>
> Please let me know how to sort the list of Stringin either ascending / descending order without considering
> special characters and case.
> ex: list1=['test1_two','testOne','testTwo','test_one']
> Applying the list.sort /sorted method results in sorted list ['test1_two', 'testOne', 'testTwo', 'test_one']
> but the without considering the special characters and case it should be
> ['testOne','test_one', 'test1_two','testTwo'] OR ['test_one','testOne','testTwo', 'test1_two' ]
>
> list.sort /sorted method sorts based on the ascii value of the characters but Please let me knwo how do i
> achievemy expected one

You can pass a key function into list.sort() and sorted(). This
allows you to customize the sorting. In the below examples
I use lambda but you can use a non-lambda function (if youneed
more complexity).

Case insensitive searches are often done by converting the
strings being compared into the same case. Here I turned
them all uppercase.

lst = ['test1_two', 'testOne', 'testTwo', 'test_one']
lst.sort(key=lambda x: x.upper())

This will filter non-alphanumeric characters. You may
be able to create and use a translation table instead.

lst.sort( key=lambda x: ''.join( c.upper() for c in x if c
in string.letters+string.digits ) )

~Ramit

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