swap 2 letters in python

[Rudi Hammad]

hello,
first of all, happy new year!!!
this is my first 2016 question. I have a list like myList=[ 'l_pollexFeatherWingA_loc', 'l_primCovFeathers1AEnd_loc', 'l_primCovFeathers1A_loc', 'l_primCovFeathers2AEnd_loc']
actually, the list is a lot longer but that will work. I want to swap "1A" and to "2A" , to "A1" and "A2". The first element "l_pollexFeatherWingA_loc" is fine because it doesn´t have a number before.
I tried using split, but I can´t figure it out, because the elements of the list are too different. Just swapping "number+Letter" to "letter+number" would be perfect, but I guess it is not possible.
I search on google, but the solutions I found didn´t work for me.
cheers!

[Phil Sloggett]

regex will be your friend here. Dont bother trying to learn all of regex, but knowing some basic patterns are very handy for exactly this situation (and figure out more complicated ones if/when you need to). For instance, to match a number followed by a single capital letter you could use a pattern like:

"([0-9][A-Z])"

The [0-9] is literally "match any digit", and the [A-Z] means match any capital letter right after it. If you want to include lower case letters then you could use [A-Za-z]. Wrapping the whole thing in brackets "()" means you get a "group" containing the match, which you can use to find/replace later.

some working code to play with:

import re
item = 'l_primCovFeathers1AEnd_loc'
pattern = "([0-9][A-Z])"
match = re.search(pattern, item)
if match:
    letter_number = match.group(0)
    number_letter = letter_number[::-1]
    new_item = item.replace(letter_number, number_letter)
    print new_item
else:
    print "NO MATCH: %s" % item

Hope that's useful! In terms of regex worth knowing offhand, I'd recommend learning what the basic characters are and how to use them i.e. [] {} () ^ $ . + *    .... They get me by in 99% of situations.

Phil

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[Justin Israel]

Also, there is a re.sub() for doing regex substitutions

https://docs.python.org/2/library/re.html#re.sub

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[Rudi Hammad]

How do you know all that stuff??!! XD
Wow, thanks. There is no way I would have found that on my own

[Rudi Hammad]

[Marcus Ottosson]

How do you know all that stuff??!! XD

Whenever you think “string manipulation” beyond the simple replace() or upper(), think “Regular Expressions” (aka “regex” or “re”) and you’ve got it. :)

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[Justin Israel]

On Mon, Jan 4, 2016 at 10:32 PM Rudi Hammad <rudih...@gmail.com> wrote:

How do you know all that stuff??!! XD
Wow, thanks. There is no way I would have found that on my own

At one point, any of us would have asked the same question. I found the answers through searching or asking. Over time you just build up a ton of answers in your brain and become more and more productive. 

Basically... time.

 

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[Rudi Hammad]

Sometimes it is overwhelming to see how much stuff people knows. But it is cool. It keeps me wanting to know more ( until you trough me out from this forum because I keep asking XXXD)

El lunes, 4 de enero de 2016, 21:55:09 (UTC+1), Justin Israel escribió:

On Mon, Jan 4, 2016 at 10:32 PM Rudi Hammad <rudih...@gmail.com> wrote:

How do you know all that stuff??!! XD
Wow, thanks. There is no way I would have found that on my own

At one point, any of us would have asked the same question. I found the answers through searching or asking. Over time you just build up a ton of answers in your brain and become more and more productive. 

Basically... time.

 

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