HoW count sequences in Python

Question

I have a series like below. The series is a dataframe. I convert to a series just to show here.

Responses = {N, N, N, N, N, S, N, N, N, N, N, N, S, N, N, N, N, N, N, N, N, N, N, N, N, N, S, S, S, S, S, S, N, N, S, N, N, N, S, S, S, S, N, S, N, N, N, N, N, N, N, S, S, N, N, N, S, S, S, N, S, S, S, S, S, S, S, S,N, N, N, N, N, S, N, N, N, N, N, N, S, N, N, N, N, N, N, N, N, N, N, N, N, N, S, S, S, S, S, S, N, N, S, N, N, N, S, S, S, S, N, S, N, N, N, N, N, N, N, S, S, N, N, N, S, S, S, N, S, S, S, S, S, S, S, S }

I use this code to count the largest sequence of 'S' (I know that this is not the best way):

import csv
import numpy as np
import pandas as pd

df = pd.read_csv('C:\\teste\\pergunta.csv')

count = 0
prev = 0
indexend = 0
indexcount = 0
for i in range(0,len(df)):
    if df['Responses'].loc[i] == 'S':
        count += 1
        indexcount = i
    else:
        if count > prev:
            prev = count
            indexend = i
        count = 0

if count > prev:
    prev = count
    indexend = indexcount

print("The longest sequence is "+str(prev))
count = 0
prev = 0
indexend = 0
indexcount = 0

The code says that the longest sequence os 'S' is 8. This is ok.

But, this sequence of 8 S happens twice.

My question: I need a code that counts individual sequences of S from the longest to the minimum.

Something like:

Sequence	Frequency
8	2 times
7	1 times
6	3 times
5	1 times
4	x times
3	x times
2	x times

Can someone help me?

Thanks

Answer 1

Try this:

s = pd.Series(Responses)
s = s.loc[s.eq('S')].groupby(s.ne(s.shift()).cumsum()).count().value_counts()
df = s.map('{} times'.format).rename_axis('Sequence').reset_index(name = 'Frequency')

or

m = df['Responses'].eq('N')

df.groupby(m.cumsum().mask(m))['Responses'].count().value_counts().astype(str).add(' times').rename_axis('Sequence').reset_index(name = 'Frequency')

Output:

   Sequence Frequency
0         1   8 times
1         6   2 times
2         4   2 times
3         2   2 times
4         3   2 times
5         8   2 times