python for循环计数器返回0

Question

Please excuse my noobishness. I've been hitting the python books and websites for the past 6 months because I really, really want to learn it, but occasionally I'll hit a road block where I just don't get why the simplest code won't work.

I've looked at quite a few stack overflow answers on this, to no avail.

I'm working on some exercises that explicitly require the use of a python for loop counter system (I know there is such a thing called itertools and enumerate). Please see below:

>>> a = raw_input('Please enter a 7-digit number: ')    
Please enter a 7-digit number: 7893848    
>>> b = raw_input('Please enter a single digit number: ')    
Please enter a single digit number: 8    
    for i in a:            
        count = 0            
        if i == b:                
            count += 1            
        print count

output:

0
1
0
0
1
0
1

How do I just get it to return the sum of 3 that - that is, the number of 8's in variable a?

Answer 1

You are setting your counter to zero in every loop cycle. You have to define it outside the loop. Try:

c=0
for i in range(10):
    print c    
    c+=1

If you only want to print the number of times 8 is in the variable, you also have to keep the print statement outside the loop, so it would print only after the loop has been exhausted:

a='7893848'
b='8'
count=0
for i in a:
    if i==b:
        count+=1
print count

Answer 2

Python string objects have a count() method which does what you need:

print(a.count('8'))

or

print(a.count(b))

Should do it.