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# 1.7 Comments

Last on my to-do list is the death rate, which is the number of deaths divided by the population.

Figure 6

A quick glance at the WHO website tells me Portugal’s population in 2013.

In []:

populationOfPortugal = 10608

Wait a minute! This can’t be right. I know Portugal isn’t a large country, but ten and a half thousand people is ridiculous. I look more carefully at the WHO website. Oh, the value is given in thousands of people; it’s 10 million and 608 thousand people. I could change the assignment to

In []:

populationOfPortugal = 10608000

but that could give the impression that the population had been counted exactly, whereas it’s more likely the number is an estimate based on a previous census. It also makes it easier to check my code against the WHO data if I use the exact same numbers.

I will therefore keep the original assignment but make a note of the unit, using a comment , a piece of text that documents what the code does.

In []:

# population unit: thousands of inhabitants

populationOfPortugal = 10608

# deaths unit: inhabitants

deathsInPortugal = 140

A comment starts with a hash sign (#) and goes until the end of the line. Computers ignore all comments, they just execute the code. Comments are your insurance policy: they help you understand your own code if you come back to it after a long break.

I can now compute the death rate, making sure I first convert the population into number of inhabitants, the same unit as deaths.

In []:

deathsInPortugal / (populationOfPortugal * 1000)

Out[]:

1.3197586726998491e-05

The death rate (roughly 140 people in 10 million) is a very small number, not very practical to display and reason about. Looking again at the WHO website, I note that other indicators, like TB prevalence, are given per 100 thousand inhabitants. I will do the same for the death rate. Since the population is already in thousands, dividing the deaths by the population gives me the number of deaths per thousand people. Thus, the number of deaths per 100 thousand people must be 100 times higher than that.

In []:

# death rate: deaths per 100 thousand inhabitants

deathsInPortugal * 100 / populationOfPortugal

Out[]:

1.3197586726998491

This finishes the basics of coding needed for this week. It took less than 30 lines of code…

Test this out for yourself in Exercise 4 of the Week 1 exercise notebook.

## Exercise 4 Comments

Complete the short exercise on the death rate in Exercise 4 in the Week 1 Exercise notebook.

Remember that once the notebook is open, run all the code, before doing the exercise.