Why One of the Arrays had an error checking when I tried to count the number of numbers in an array using python

Question

So I tried to do something like counting how many occurances in an array and then saves those values on to Dictionary, but along the way there is one values that has wrong counts. When I did some tracing with the code I noticed that this value suddenly restarted the counting. Tried to search on the web but I didn't found it or I didn't search that deep.

Code :

listA = [11, 45, 8, 11, 101, 23, 45, 23, 45, 89, 101]
dictList = {
    
}

n = len(listA)

for i in range (0, n):
    total = 1
    if listA[i] not in dictList:
        dictList[listA[i]] = total
    else:
        for j in range (i, n):
            if listA[i] == listA[j]:
                total = total + 1
        dictList.update({listA[i] : total})

print(dictList)

The output it given :

{11: 2, 45: 2, 8: 1, 101: 2, 23: 2, 89: 1}

The correct output :

{11: 2, 45: 3, 8: 1, 101: 2, 23: 2, 89: 1}

Yes, it was just one variable that got wrong. Thank you in advance

question from:https://stackoverflow.com/questions/65867833/why-one-of-the-arrays-had-an-error-checking-when-i-tried-to-count-the-number-of

Answer 1

Here are several ways of counting elements in a list

list_to_count = [11, 45, 8, 11, 101, 23, 45, 23, 45, 89, 101]

# Basic dict operations
counts = {}
for x in list_to_count:
    if x not in counts:
        counts[x] = 1
    else:
        counts[x] += 1

# Using .get()
counts = {}
for x in list_to_count:
    counts[x] = counts.get(x, 0) + 1

# Using .setdefault()
# Pretty much the same as .get() but useful when the default is a mutable object like a list or dict
counts = {}
for x in list_to_count:
    counts[x] = counts.setdefault(x, 0) + 1

# Using collections.Counter (the simplest solution...)
from collections import Counter
counts = Counter(list_to_count)