Python count function - Get the number of item in a list

You can get the occurrence of an item in a list.

p = ['a', 'a', 'a', 'b', 'c', 'c']

i = p.count('a')

print(i)  # 3

count returns the number of a in p. There are 3 a in p so 3 is returned.

Python count and len are confusing as follows.

p = ['a', 'a', 'a', 'b', 'c', 'c']

i = p.count('a')
j = len(p)

print(i)  # 3
print(j)  # 6

No item, 0 count

If the list doesn't contain the item, count returns 0.

p = ['a', 'a', 'a', 'b', 'c', 'c']

i = p.count('d')

print(i)  # 0

There is no d in p list so count returns 0.

If an item is a list...

count works for a list, set, dictionary, and so on.

a = [1, [2, 3], 'car']

c = a.count([2, 3])

print(c)  # 1

a has actually [2, 3] but doesn't have 2 itself. [2, 3] and 2 are essentially different in Python.

a = [1, [2, 3], 'car']

c = a.count(2)

print(c)  # 0

Substring occurrence

You can use count to count how many times the substring occurs in a string.

s = 'aabbbcccc'

a = s.count('a')
b = s.count('b')
c = s.count('c')

print(a)  # 2
print(b)  # 3
print(c)  # 4

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