您如何计算列表中某个模式的出现次数？

Question

Assume I have the following list: ['b(2)','b(6)','a(3)','z(8)',b(4)] And I want to count how often this list contains b(*), with * being any number. How would I achieve such thing in python?

Answer 1

Hope this helps:

import re
a = ['b(2)','b(6)','a(3)','z(8)','b(4)']
count = sum([1 for i in a if len(re.findall('b\([0-9]\)',i))==1])
print(count)

Answer 2

One way to do it without using RegEx if the values are always in the above format:

# Get the lenght of a list of items in list l if the item (i) contains b
l = ['b(2)','b(6)','a(3)','z(8)','b(4)']    
print(len([i for i in l if "b" in i]))

Or

import re
l = ['b(2)','b(6)','a(3)','z(8)','b(4)']
# Get the lenght of a list of items in list l if the item (i) matches the regex b\([0-9]\)
print(len([i for i in l if re.search(r'b\([0-9]\)', i)]))

Output:

3