I was trying to write a letter repetition counting function but it is not working

The function is supposed to take a string like:

'kkikkd'


and return a list of the letters and their repetitive values i.e.

[[k,2],[i,1],[k,2],[d,1]]


but it isn't working. Any ideas?

def chnum(xtrr):
lis2 =
for n in xtrr:
if lis2[0][0] == n:
continue
lis1 = [n]
for m in xtrr:
if n == m:
i += 1
lis1 += [i]
lis2 += [lis1]
return lis2


3 Answers
3

If I have got your question correctly then you are trying to keep count of each character in a string and store the result in a list. The brute force way of doing is using a dictionary to keep track of character and number of times it has appeared.
Here is the code:

st= "kkikkd"
l=
temp=1
for i in range(1,len(st)):
if st[i-1] == st[i]:
temp += 1
else:
l.append([st[i-1],temp])
temp= 1
if st[i] == st[i-1]:
temp += 1
l.append([st[i],temp])


output: [['k', 2], ['i', 1], ['k', 2], ['d', 1]]

string = "kkikkd"

[[k,2],[i,1],[k,2],[d,1]]

'kkikkd'

st= "kkikkd"

You can use itertools.groupby

itertools.groupby

>>> from itertools import groupby
>>> s = 'kkikkd'
>>> [[k, len(list(v))] for k,v in groupby(s)]
[['k', 2], ['i', 1], ['k', 2], ['d', 1]]


Alternatively you can also use re.findall to do this

re.findall

>>> import re
>>> [[k, len(v)] for v,k in re.findall(r'((.)2*)', s)]
[['k', 2], ['i', 1], ['k', 2], ['d', 1]]


To begin with, there are 2 problems in your code

def chnum(xtrr):
lis2 =
for n in xtrr:
if lis2[0][0] == n: # lis2 is empty. It does not have 0th element, much less another nested list.
# this will only check if n is in the first element of lis2, what about all the other elements?
continue
lis1=[n]
i = 0
for m in xtrr:
if n== m:
i+=1
lis1 += [i]
lis2 += [lis1]
return lis2
print(chnum('kkidduus'))


But instead of fixing it I would advise to use the power of python. In particular its dictionaries
like so:

def chnum(xtrr):
d = n:0 for n in xtrr # create a dict where keys are letters from input string
for n in xtrr:
d[n] += 1
# for each letter from input increment the dict's value for that letter
return d

print(chnum('kkidduus'))


You will see how much more concise and readable this code is.
if you are really adamant about getting results as nested lists then this dictionary is also a good starting point. Just dol = [list(t) for t in chnum('kkidduus').items()] afterwards

l = [list(t) for t in chnum('kkidduus').items()]

EDIT:
the OP wants to see counts at every repetition of the letter, so the code above can be modified to accomodate that

def chnum(xtrr):
d = n:0 for n in xtrr # create a dict where keys are letters from input string
for n in xtrr:
d[n] += 1
# for each letter from input increment the dict's value for that letter
l = [[n, d[n]] for n in xtrr]
return l

print(chnum('kkidduus'))


using a dictionary still has merit here as dict keys are hashed and thus will have speed advantages when counting letter occurence

print(chnum('kkikkd'))

By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.