如何在列表的列表中多次索引某个字符？

Question

I am reading in numbers from a csv file and attempting to count each time the number '1' occurs in the first column of the file.

f = open(fileName, 'r')
reader = csv.reader(f)

votes = []
count = 0

for row in reader:
    votes.append(row)

for i in votes:
    if votes[0:i] == '1':
        count += 1

print(count)

This is the error i receive:

TypeError: slice indices must be integers or None or have an __index__ method

Answer 1

You don't need to do this with a slice. If the first character in a line is 1 then line[0] == 1 will be True.

You can simple sum the booleans by taking advantage of the fact that python treats True and False as 1 , and 0 allowing you to sum things like sum([True, True, False, 0, 1]) which evaluates to 3

Given a file at path like:

123
234
143

454
16786

111

You can simply do:

with open(path) as f:
    total = sum(l[0] == '1' for l in f)
    
print(total)
# prints: 4