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Python Python Collections (Retired) Dictionaries Word Count

zachary hatsis
zachary hatsis
1,072 Points
Posted by zachary hatsis
zachary hatsis
1,072 Points

word_count() problem in python collections. stuck!

I am stuck on this one. How do i increment the key value of a key for how many times it has occured?

word_count.py 
# E.g. word_count("I am that I am") gets back a dictionary like:
# {'i': 2, 'am': 2, 'that': 1}
# Lowercase the string to make it easier.
# Using .split() on the sentence will give you a list of words.
# In a for loop of that list, you'll have a word that you can
# check for inclusion in the dict (with "if word in dict"-style syntax).
# Or add it to the dict with something like word_dict[word] = 1.

my_dict = {}


def word_count(mystring):
  mystring = mystring.lower().split()
  dict_count = 0
  for i in mystring:
    my_dict[i] = None
    if i in my_dict:
      my_dict[i] += 1
  return my_dict
zachary hatsis
zachary hatsis
1,072 Points
zachary hatsis
zachary hatsis
1,072 Points

This is getting me closer, however once it iterates through the first 'i am that' it stops iterating over the last 'i am'

my_dict = {}
mystring = 'I am that i am'

def word_count(mystring):
  mystring = mystring.lower().split()
  dict_count = 0
  for i in mystring:
    my_dict[i] = 0
  for i in my_dict: 
    if i in my_dict:
      my_dict[i] += 1
  return my_dict

word_count(mystring)

2 Answers

Frederick Pearce
Frederick Pearce
10,677 Points
Frederick Pearce
Frederick Pearce
10,677 Points

There seems to be an extra loop in there over the dictionary that I suspect is the issue. Hanley Chan's answer should work, or something similar. The code below passed and is pretty compact. Good luck!

def word_count(mystring):
    my_dict = {}
    for string in mystring.lower().split():
        if string not in my_dict:
            my_dict[string] = 1
        else:
            my_dict[string] += 1
    return my_dict
Hanley Chan
Hanley Chan
27,771 Points
Hanley Chan
Hanley Chan
27,771 Points

Hi,

When you loop through your mystring list you could check whether each word is already in your dictionary or not. If yes, increment your counter by one otherwise set it equal to one.

for i in mystring:
    if i in my_dict:  
      my_dict[i] += 1
    else:
      my_dict[i] = 1
zachary hatsis
zachary hatsis
1,072 Points
zachary hatsis
zachary hatsis
1,072 Points

When you try to do my_dict[i] += 1 you get:

TypeError: unsupported operand type(s) for +=: 'NoneType' and 'int'

Hanley Chan
Hanley Chan
27,771 Points
Hanley Chan
Hanley Chan
27,771 Points

Did you remove the line 

my_dict[i] = None

It looks like it's throwing an exception because you are trying to increment None.

zachary hatsis
zachary hatsis
1,072 Points
zachary hatsis
zachary hatsis
1,072 Points

if i remove my_dict[i] = None it doesn't convert the list in 'mylist' to a dictionary.