How to get for every letter of sentence an index of letter?-CodePudding

I want to get every letter and their index. But I got the wrong answer.

def counting(sentence):
    for letter in sentence:
        if not letter == ' ':
            print(letter ,":", [sentence.index(letter)],end ="    ")
print(counting("Hello my friends"))
H : [0]    e : [1]    l : [2]    l : [2]    o : [4]    m : [6]    y : [7]    f : [9]    r : [10]    i : [11]    e : [1]    n : [13]    d : [14]    s : [15]

I got this as an answer. The problem is that I got double e but with the same index. The idea is to get for example e:[1,19,24 etc.]. What should I change? Is a possibility to make it with dictionary?

CodePudding user response：

You could use enumerate to loop over the string and give both the element and also the index number.

This also uses a defaultdict in order to have a dictionary containing lists as values, where if the key does not already exist then it will be created as an empty list when you call append.

from collections import defaultdict

sentence = "Hello my friends"

indexes = defaultdict(list)

for index, letter in enumerate(sentence):
    if letter != ' ':
        indexes[letter].append(index)

for letter in sorted(indexes):
    print(f"{letter}: {indexes[letter]}")

This gives:

H: [0]
d: [14]
e: [1, 12]
f: [9]
i: [11]
l: [2, 3]
m: [6]
n: [13]
o: [4]
r: [10]
s: [15]
y: [7]

UPDATE: in response to a comment below saying that the output indexes should not increment on spaces: this is not my interpretation of the question, but if this is intended, it can be dealt with by pre-processing the input:

sentence = sentence.replace(" ", "")

(and then the if condition becomes unnecessary and could be removed).

CodePudding user response：

Instead of searching for a letters index in-line, you can just store the current index as a local variable.

def counting(sentence):
    current_indx = 0
    for letter in sentence:
        if not letter == ' ':
            print(f'{letter} : [{current_indx}]',end ="    ")
        current_indx  = 1

CodePudding user response：

or you can do like this:

def counting(sentence):
    res = {key: [] for key in set(sentence)}
    for i in range(len(sentence)):
        if not sentence[i] == ' ':
            res[sentence[i]].append(i)
    return res
print(counting("Hello my friends"))