# Guided Project: Exploring Hacker News Posts - Slide 5

Below is the solution to this guided project, my challenge is, can someone please explain the logic behind this line of code -> comments_by_hour[time] += comment

# Calculate the amount of ask posts created during each hour of day and the number of comments received.

import datetime as dt

result_list =

result_list.append(
[post[6], int(post[4])]
)

counts_by_hour = {}
date_format = “%m/%d/%Y %H:%M”

for each_row in result_list:
date = each_row[0]
comment = each_row[1]
time = dt.datetime.strptime(date, date_format).strftime("%H")
if time in counts_by_hour:
counts_by_hour[time] += 1
else:
counts_by_hour[time] = 1

This is like saying `comments_by_hour[time] = comments_by_hour[time]+comment`. `+=` (also known as addition assignment) adds another value with the `comments_by_hour[time]`'s value and assigns the new value to the `comments_by_hour[time]`.

It is easier to understand this logic using variables:

``````>>> age = 20
>>> age = age + 1
>>> print(age)
21
``````

We can rewrite the above code using the addition assignment

``````>>> age = 20
>>> age += 1
>>> print(age)
21
``````

Okay, I do understand the logic you explained, but in this case, this is making a dictionary. Here’s the link, so you can have a wholistic view of the concept I’m having issues with. My question is in the 6th cell. https://github.com/dataquestio/solutions/blob/master/Mission356Solutions.ipynb

Total number of comments at a given hour.

Okay, thank you so much. It’s now clear.

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