Calculating the number of characters inside a list in python-CodePudding

I made a list with some character in it and I looped through it to calculate the number of a specific character and it returns the number of all the characters inside the list and not the one's that I said it to. Take a look at my code and if someone can help I will appreciate it!

This is the code:

array = ['a', 'b', 'c', 'a']
sum_of_as = 0
for i in array:
    if str('a') in array:
        sum_of_as  = 1
        
print(f'''The number of a's in this array are {sum_of_as}''')

CodePudding user response：

The most pythonic method would be to use sum() generator.

list_of_strings = ["a", "b,", "c", "d", "a"]
count = sum(string.count("a") for string in list_of_strings)
print(count)

>>> 2

The above iterates each element of the the list and totals up (sums) the amount of times the letter "a" is found, using str.count()

str.count() is a method that returns the number of how many times the string you supply is found in that string you call the method on.

name = "david"
print(name.count("d"))

>>> 2

This is the equivalent of doing

count = 0
list_of_strings = ["a", "b,", "c", "d", "a"]
for string in list_of_strings:
    count  = string.count("b")
print(count)

If you know the list is only ever going to contain single letter strings, as per your example, or if you are searching for a word in a list of words, then you can simply use list_of_strings.count("my_string").

Be aware though that will not count things such us l = ["ba", "a", "c"] where the response would be 1 as opposed to 2. The top examples do account for this, so it really does depend on your data and use case.

CodePudding user response：

The if str('a') in array evaluates to True in every for-loop iteration, because there is 'a' in the array.

Try to change the code to if i == "a":

array = ["a", "b", "c", "a"]

sum_of_as = 0
for i in array:
    if i == "a":
        sum_of_as  = 1

print(sum_of_as)

Prints:

OR:

Use list.count:

print(array.count("a"))