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Introduction to Python
course content

Course Content

Introduction to Python

Introduction to Python

1. First Acquaintance
The Very First StepsCommentsSome Simple MathMore Challenging MathChallengeBringing It All Together
2. Variables and Types
Storing NumbersNaming RulesUsing VariablesData TypesNumbersChallengeStoring TextString IndexingNegative Indexing and LengthString SlicingChallengeConcatenation
3. Conditional Statements
Boolean Data TypeChallenge: Comparison OperatorsCombining ConditionsChallenge: Logical OperatorsMembership Operators and Types ComparisonSimple if/else ExpressionsChallenge: Grocery StoreChallenge: Odd and Evenif/elif/else ExpressionsChallenge: Grocery Store ExtendedChallenge: Positive, Negative or Zero
4. Other Data Types
What Is a List?List MethodsChallengeNested ListsChallengeWhat Is a Tuple?Tuple MethodsChallengeNested TuplesChallengeWhat Is a Dictionary?ChallengeDictionary MethodsChallenge
5. Loops
while LoopChallengefor LoopChallengeRangeChallengeIterating Over IndexesNested Loops
6. Functions
Built-in FunctionsChallengeDefining Your First FunctionChallengeif/else Statements in FunctionsChallengeFunctions With No ReturnChallengeModifying FunctionsChallengeLambda FunctionsChallenge

bookFunctions With No Return

Up until now, we've always returned some kind of information from our functions. However, it's not always necessary to return and store values after a function completes its task. Sometimes, you might just want to display something.

Let's say we have a dictionary named countries_dict that holds data in the format country: (area, population). We can create a function that takes two arguments: d (intended to be a dictionary) and name (intended to be a key in that dictionary). This function won't return any value; instead, it will just print the data in a user-friendly format.


              
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# Data
countries_dict = {'USA': (9629091, 331002651), 'Canada': (9984670, 37742154), 
                  'Germany': (357114, 83783942), 'Brazil': (8515767, 212559417), 
                  'India': (3166391, 1380004385)}

# Defining a function
def country_information(d, name):
  print('Country:', name)
  print('Area:', d[name][0], 'sq km')
  print('Population:', round(d[name][1]/1000000, 2), 'MM')

# Testing the function
country_information(countries_dict, 'Brazil')
country_information(countries_dict, 'Germany')
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Note

In this code, d represents a parameter in the function country_information(d, name). When country_information function is called, countries_dict is passed to the function with name d, which holds data about various countries. Inside the function, d[name][0] accesses the area and d[name][1] accesses the population for the specified country.

Thus, d is essentially a copy of the variable (countries_dict here) that was passed to that position when the function was called.

From the example, you'll notice that the function contains two parameters that aren't explicitly defined in the code. These are local variables, and they can't be accessed outside of the function. However, when you invoke the function (as shown in the last two lines), countries_dict is used as the d variable, and 'Brazil'/'Germany' serves as the name.

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Section 6. Chapter 7
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