如何计算嵌套列表中两个项目的出现次数

Question

I have a nested list

a = [[1,'a','b'], [2,'c','d'], [3,'a','b']]

how can i count the number of occurrences that a & b appeared in the nested list?

in this case the answer shall be 2 times.

ps this is my first time post, so thanks for all the help.

Answer 1

You can test for inclusion in a list with

'a' in some_list

This will be true or false. You can make multiple tests with and (there are also some other ways that may be a little prettied):

'a' in some_list and 'b' in some_list

This will be true if both conditions are met. To do this for all the lists in your list you can use a list comprehension:

a_list = [[1,'a','b'], [2,'c','d'], [3,'a','b']]

['a' in x and 'b' in x for x in a_list]

This will return a list of boolean values, one for each item in your list:

[True, False, True]

When treated like numbers python treats True as 1 and False as 0 . This means you can just sum that list to get you count and have a solution in one line:

a_list = [[1,'a','b'], [2,'c','d'], [3,'a','b']]

sum(['a' in x and 'b' in x for x in a_list])
# 2