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Python Python Collections (Retired) Dictionaries Word Count

Posted by Thomas Katalenas
Thomas Katalenas
11,033 Points

word_count(arg): i cant add to dictionary i tried everything!!?

def word_count(arg): type(arg) == str p = arg.split() count = 0 for i in p: j = p.pop() count += 1 word_dict = dict([(j, count)]) return word_dict

I can not figure this out, big problem plus the poping isn't working right, im sick of it.

my head hurts. can you help me?

4 Answers

Chris Freeman
MOD
Chris Freeman
Treehouse Moderator 68,454 Points
Chris Freeman
Chris Freeman
Treehouse Moderator 68,454 Points

Let's look at your code first:

def word_count(arg):
  # this is a Boolean statement not assigned to a variable
  # type checking not necessary for challenge
  type(arg) == str
  # Split arg into words on whitespace
  p = arg.split()
  # initialize count to zero
  count = 0 
  # for each item i in wordlist p
  for i in p:
    # pop item off of p
    # this also shortens p causing loop to end sooner
    j = p.pop()
    # increment count
    # count is same as item's index in p
    count += 1
    # assign a new dict to word_dict
    # overwrites word_dict every loop
    word_dict = dict([(j, count)])
  # return last word_dict
  return word_dict

Let now break the task down

# Create a function named word_count()
# that takes a string [as an argument]
def word_count(arg):
    # Return a dictionary
    word_dict = {}
    # with each word in the string
    for word in arg.split():
        # check if word has been seen (already in dict key list)
        if word in word_dict:
            # increment count
            word_dict[word] += 1
        else:
            # initialize new word in dict
            # word as the key and the number of times it appears as the value
            word_dict[word] = 1
    return word_dict

The difficulty in using a snippet of code without fully understanding why it works can be confusing when using the same snippet in a different context.

The syntax dict([(j, count)]) is legal, but reassign it to word_list will overwrite the previously created dictionary.

>>> words = ['first', 'second', 'last']
>>> for word in words:
...     pass
... 
>>> count = 0
>>> for word in words:
...     word_list = dict([(word, count)])
...     print(word_list) 
...     count += 1
... 
{'first': 0}
{'second': 1}
{'last': 2}
>>> print(word_list)
{'last': 2}

Instead of overwritting word_list you can update it with the additional dict:

>>> word_list = {}
>>> count = 0
>>> for word in words:
...     word_list.update(dict([(word, count)]))
...     print(word_list) 
...     count += 1
... 
{'first': 0}
{'second': 1, 'first': 0}
{'second': 1, 'first': 0, 'last': 2}
>>> print(word_list)
{'second': 1, 'first': 0, 'last': 2}

Note: The above example is using the incorrect count values from original post.

Shadow Skillz
Shadow Skillz
3,020 Points
Shadow Skillz
Shadow Skillz
3,020 Points

Hey Chris just want to thank you for the easy break down I looked over most of the examples but still couldn't wrap my head around the concept but you explained it perfectly thanks

Clara McKenzie
Clara McKenzie
691 Points
Clara McKenzie
Clara McKenzie
691 Points

my answer was rejected but it works fine in my MacOS intepreter:

def word_count( thestr ):
    index=0
    mydict={}
    mylist=thestr.split()
    while (index < len(mylist)):
        mydict[ mylist[index] ] = thestr.count(mylist[index])
        index += 1
    return mydict

[MOD: added ```python formatting -cf]

Chris Freeman
Chris Freeman
Treehouse Moderator 68,454 Points
Chris Freeman
Chris Freeman
Treehouse Moderator 68,454 Points

You are very close. In your code you need the count on mylist instead of thestr:

def word_count( thestr ):
    index=0
    mydict={}
    mylist=thestr.split()
    while (index < len(mylist)):
        mydict[ mylist[index] ] = mylist.count(mylist[index])
        index += 1
    return mydict
Thomas Katalenas
Thomas Katalenas
11,033 Points
Thomas Katalenas
Thomas Katalenas
11,033 Points

see the dict([(j, count)]) approach was confusing it was at the bottom of one of the videos dict( key, value)

but it does'nt work for me when I try the increment, it wants to return two values error. So I don't know the Python API is confusing and ambiguous in the docs which is why I really like python syntax is clear and concise but the API documentation is not as transparent as i would like, what do you think? Although I am learning Julia programming it is nice! it clearly helps you learn machine learning algorythms

Chris Freeman
Chris Freeman
Treehouse Moderator 68,454 Points
Chris Freeman
Chris Freeman
Treehouse Moderator 68,454 Points

The difficulty in using a snippet of code without fully understanding why it works can be confusing when using the same snippet in a different context.

I have updated my answer to add a way to use the dict([(j, count)]) approach.

Thomas Katalenas
Thomas Katalenas
11,033 Points
Thomas Katalenas
Thomas Katalenas
11,033 Points

have you done this before? ;b