Python：计算列表中的项目组

Question

I am working on learning Python via Codecademy and I am struggling to figure out why I am getting a return of 1 when I run this query. Note: I know I could do a sequence.count(item) but I am trying to do this without the count function. Any help would be appreciated.

def count(sequence, item):
    rep = int(0)
    for item in sequence:
        if item in sequence:
            rep += 1
        else:
            rep = 0
    return rep

print count([1], 7)

Answer 1

I think you confused yourself by using "item" to refer to two different things. I changed the loop variable to i .

def count(sequence, item):
    rep = 0
    for i in sequence:
        if i == item:
            rep += 1
    return rep

print count([1], 7)

Also, you probably don't want to keep setting rep to 0

Answer 2

Corrected function:

def count(sequence, item):
    rep = 0
    for i in sequence:
        if i == item:
            rep += 1
    return rep

Regarding these lines:

for item in sequence:
    if item in sequence:

When you input [1] into the function, it goes:

• for item in sequence (first and only item is 1 )

• if item is in sequence ( if 1 is in the sequence... which it is)

• then rep += 1 , hence 1 is returned

for item in sequence means for each item in the sequence , do something. In your case you are merely confirming that the item is indeed in the sequence. You are in fact never even using or considering the 7 you input.