Question

I am looking to create a program in python that asks the user to enter a list of numbers in [] format.

It then must count and display how many of those numbers in the list are between 1 and 10, 10 and 20,
20 and 30.

Each section of 10 are to be counted whether or not there is a number within that section meaning it can return a 0.

Here is what I have so far.

the_input = raw_input("Enter numbers... ") 

the_list = [int(x) for x in the_input.strip("[]").split(",")] 

group_counter = {} 

for number in the_list:
    group_start = (number // 10) * 10 
    group_end = group_start + 9 
    group_name = "%s-%s" % (group_start, group_end) 

    group_counter.setdefault(group_name, 0) 
    group_counter[group_name] += 1 

for name, count in group_counter.items():
    print "There were %s in %s" % (count, name)

Answer 1

collections.Counter is your friend here.

import collections

the_input = raw_input("Enter numbers... ") 
the_list = [int(x) for x in the_input.strip("[]").split(",")] 
group_counter = collections.Counter(x//10 for x in the_list)
bin_range = xrange(min(group_counter.keys()), max(group_counter.keys()) + 1)
for bin_tens in bin_range:
    print "There were {} in {} to {}".format(group_counter[bin_tens], bin_tens*10, bin_tens*10+9)

Edit: If you want the printed counts to only show for 0-9 to 90-99, then just change the bin_range line to bin_range = range(10)