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Introduction to Python(ihor)
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Introduction to Python(ihor)

Introduction to Python(ihor)

1. First Acquaintance with Python
The Very First Steps in PythonHow to Use Comments for ReadabilityPerform Simple Math in PythonHandle More Complex Math in PythonBringing Python Fundamentals Together
2. Variables and Types in Python
How to Store Numbers in PythonPython Naming Rules for VariablesHow to Work with Variables in PythonData Types in PythonChallenge: Converting Kilometers to MilesStore Text with Strings in PythonString Indexing in PythonString Slicing in PythonChallenge: Retrieving Letters from StringString Concatenation in Python
3. Conditional Statements in Python
Boolean Data Type in PythonChallenge: Working with Comparison OperatorsHow to Combine Conditions in PythonChallenge: Working with Logical OperatorsMembership Operators and Type Comparisons in PythonHow to Use if/else Expressions in PythonChallenge: Running a Grocery StoreChallenge: Creating Odd and Even Logicif/elif/else ExpressionsChallenge: Running Grocery Store ExtendedChallenge: Weather Adviser
4. Other Data Types in Python
Python ListsCommon List Methods in PythonChallenge: Updating ListNested Lists in PythonChallenge: Retrieving Information from Nested ListPython TuplesCommon Tuple Methods in PythonChallenge: Updating TupleNested Tuples in PythonChallenge: Retrieving Information from Nested TuplePython DictionariesChallenge: Creating DictionaryCommon Dictionary Methods in PythonChallenge: Updating Dictionary
5. Loops in Python
Explore the while Loop in PythonChallenge: Working with the While LoopExplore the for Loop in PythonChallenge: Working with the For LoopRange Function in PythonChallenge: Using the Range FunctionHow to Iterate Over Indexes in PythonExplore Nested Loops in Python
6. Functions in Python
Built-in Functions in PythonChallenge: Converting HeightsHow to Create Functions in PythonChallenge: Writing First FunctionUse of if/else Statements in Python FunctionsChallenge: Identifying Positive Values Functions Without Return in PythonChallenge: Creating Logging FunctionModifying Functions in PythonChallenge: Updating Logic of the FunctionLambda Functions in PythonChallenge: Creating Lambda Function

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Built-in Functions in Python

Imagine you have to find the largest number within the list. With what you've learned, you could write a loop that compares each element to the current largest value, updating it when a bigger number is found. Fortunately, Python provides built-in functions that make this task easier and efficient.

For example, if we need to calculate the population density for a set of countries in the countries list, we simply divide the population by the land area.


              
1234567891011

            
# Initial data
countries = [["USA", 9629091, 331002651], ["Canada", 9984670, 37742154],
             ["Germany", 357114, 83783942], ["Brazil", 8515767, 212559417],
             ["India", 3166391, 1380004385]]

# Iterating over external list
for i in range(len(countries)):
    if type(countries[i]) is list:
        # Computing population density for a country
        pop_dens = countries[i][2]/countries[i][1]
        print(countries[i][0], pop_dens, 'people per km²')
copy

The list contained five nested sub-lists. A loop iterated through the main list, checking if each item was a list. If so, the population density was calculated by dividing the third item (population) by the second item (area).


              
1234567891011

            
# Initial data
countries = [["USA", 9629091, 331002651], ["Canada", 9984670, 37742154],
            ["Germany", 357114, 83783942], ["Brazil", 8515767, 212559417],
            ["India", 3166391, 1380004385]]

# Iterating over external list
for i in range(len(countries)):
    if type(countries[i]) is list:
        # Computing population density for a country
        pop_dens = round(countries[i][2]/countries[i][1], 2)
        print(countries[i][0], pop_dens, 'people per km²')
copy

However, the results were difficult to read due to more than 10 decimal places. To improve readability, you can use the round() function to limit the output to 2 decimal places. This function takes two arguments: the first is the number to be rounded, and the second specifies the number of decimal places to retain.

question mark

Which function would you use to round a number to a specific number of decimal places?

Select the correct answer

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