{"id":1697,"date":"2023-04-03T01:53:09","date_gmt":"2023-04-03T01:53:09","guid":{"rendered":"https:\/\/datmt.com\/?p=1697"},"modified":"2023-07-31T13:46:10","modified_gmt":"2023-07-31T13:46:10","slug":"day-2-control-structures-and-functions","status":"publish","type":"post","link":"https:\/\/datmt.com\/python\/day-2-control-structures-and-functions\/","title":{"rendered":"Day 2: Control Structures and Functions"},"content":{"rendered":"\n
Welcome back to our Python learning journey! Yesterday, we covered the basics of Python programming, including data types, variables, and input\/output. Today, we’ll dive into control structures and functions.<\/p>\n\n\n\n
Control Structures<\/h2>\n\n\n\n
Control structures are constructs that allow us to control the flow of our program based on certain conditions. The most common control structures are if<\/code> statements and loops.<\/p>\n\n\n\n
If Statements<\/h3>\n\n\n\n
if<\/code> statements allow us to execute code only if a certain condition is true. Here’s the basic syntax:<\/p>\n\n\n\n
if condition:\n # code to execute if condition is true\n<\/pre><\/div>\n\n\n\n
The condition<\/code> is an expression that evaluates to either True<\/code> or False<\/code>. If it’s True<\/code>, the code inside the if<\/code> statement will be executed. If it’s False<\/code>, the code will be skipped.<\/p>\n\n\n\n
Let’s look at an example:<\/p>\n\n\n\n
age = 18\n\nif age >= 18:\n print("You are an adult.")\n\n<\/pre><\/div>\n\n\n\n
In this example, we’re checking if age<\/code> is greater than or equal to 18. If it is, we print out a message saying that the user is an adult. If age<\/code> is less than 18, the message will not be printed.<\/p>\n\n\n\n
We can also add an else<\/code> clause to execute code if the condition is False<\/code>:<\/p>\n\n\n\n
age = 16\n\nif age >= 18:\n print("You are an adult.")\nelse:\n print("You are not yet an adult.")\n\n<\/pre><\/div>\n\n\n\n
In this example, if age<\/code> is greater than or equal to 18, we print out a message saying that the user is an adult. Otherwise, we print out a message saying that the user is not yet an adult.<\/p>\n\n\n\n
Let’s improve the program by taking input from the user:<\/p>\n\n\n\n
age = int(input("Hi there, please enter your age: "))\n\nif age >= 18:\n print("You are an adult.")\nelse:\n print("You are not yet an adult.")\n\n<\/pre><\/div>\n\n\n\n
When you run it, you can enter any number and you will get the result:<\/p>\n\n\n\n<\/figure>\n\n\n\n
As you can see, there is no limit on the value you can enter. In reality, age couldn’t be < 0 or greater than 200 (for now). Can you add more checks to make sure invalid values are not allowed?<\/p>\n\n\n\n
Loops<\/h3>\n\n\n\n
Loops allow us to execute a block of code repeatedly. The two most common types of loops are for<\/code> loops and while<\/code> loops.<\/p>\n\n\n\n
For Loops<\/h5>\n\n\n\n
for<\/code> loops allow us to iterate over a sequence of values. Here’s the basic syntax:<\/p>\n\n\n\n
for variable in sequence:\n # code to execute for each value in sequence\n<\/pre><\/div>\n\n\n\n
The variable<\/code> is a temporary variable that takes on each value in the sequence<\/code> one at a time. The code inside the loop is executed once for each value in the sequence.<\/p>\n\n\n\n
Let’s look at an example:<\/p>\n\n\n\n
fruits = ["apple", "banana", "cherry"]\n\nfor fruit in fruits:\n print(fruit)\n\n<\/pre><\/div>\n\n\n\n
In this example, we’re iterating over a list of fruits and printing out each one.<\/p>\n\n\n\n<\/figure>\n\n\n\n
<\/p>\n\n\n\n
While Loops<\/h5>\n\n\n\n
while<\/code> loops allow us to execute a block of code as long as a certain condition is true. Here’s the basic syntax:<\/p>\n\n\n\n
while condition:\n # code to execute while condition is true<\/pre><\/div>\n\n\n\n
The condition<\/code> is an expression that evaluates to either True<\/code> or False<\/code>. The code inside the loop is executed repeatedly as long as the condition is True<\/code>.<\/p>\n\n\n\n
In this example, we’re using a while<\/code> loop to print out the numbers from 0 to 4.<\/p>\n\n\n\n<\/figure>\n\n\n\n
Functions<\/h3>\n\n\n\n
Functions are blocks of code that can be called from other parts of the program. They allow us to organize our code into reusable chunks and make our code more modular.<\/p>\n\n\n\n
Defining Functions<\/h4>\n\n\n\n
To define a function, we use the def<\/code> keyword followed by the name of the function and its parameters (if any):<\/p>\n\n\n\n
In this example, we’ve defined a function called greet<\/code> that takes one parameter name<\/code>. The function prints out a greeting message using the value of the name<\/code> parameter.<\/p>\n\n\n\n
Calling Functions<\/h4>\n\n\n\n
To call a function, we simply use its name followed by its arguments (if any):<\/p>\n\n\n\n
This will call the greet<\/code> and greet_general<\/code> functions. Here is the output:<\/p>\n\n\n\n<\/figure>\n\n\n\n
Returning Values<\/h4>\n\n\n\n
Functions can also return values using the return<\/code> keyword. Here’s an example:<\/p>\n\n\n\n
def square(x):\n return x * x<\/pre><\/div>\n\n\n\n
In this example, we’ve defined a function called square<\/code> that takes one parameter x<\/code>. The function returns the square of x<\/code>.<\/p>\n\n\n\n
We can call this function and use its return value like this:<\/p>\n\n\n\n
result = square(5)\nprint(result) # prints 25\n<\/pre><\/div>\n\n\n\n
<\/p>\n\n\n\n
Extra tasks<\/h3>\n\n\n\n
Now that we’ve covered the basics of control structures and functions, it’s time to put them to the test with some programming challenges.<\/p>\n\n\n\n
Write a function that takes a number as an argument and returns \"odd\"<\/code> or \"even\"<\/code> depending on whether the number is odd or even.<\/h3>\n\n\n\n
This is quite a simple assignment. The only thing you may not know beforehand is how to check if a number is odd or even. The trick is to use the modulus operator. <\/p>\n\n\n\n
Here is the code:<\/p>\n\n\n\n
number = int(input("Please input a number: "))\n\nif number % 2 == 0:\n print("The number is even")\nelse:\n print("The number is odd")\n<\/pre><\/div>\n\n\n\n
Running the program would produce the following output:<\/p>\n\n\n\n<\/figure>\n\n\n\n
<\/p>\n\n\n\n
Write a function that takes a list of numbers as an argument and returns the sum of all the numbers in the list.<\/h3>\n\n\n\n
This practice helps you reinforce your knowledge of list. Here is the code for this program:<\/p>\n\n\n\n
def sum_list(numbers):\n # initialize a variable to store the sum\n total = 0\n\n # loop through the list and add each number to the total\n for number in numbers:\n total += number\n\n # return the final total\n return total<\/pre><\/div>\n\n\n\n
Let’s break down what the code does:<\/p>\n\n\n\n
\n
We define a function called sum_list<\/code> that takes one parameter numbers<\/code>. This function returns the sum of all the numbers in the numbers<\/code> list.<\/li>\n\n\n\n
Inside the sum_list<\/code> function, we initialize a variable called total<\/code> to 0<\/code>. This variable will store the sum of all the numbers in the list.<\/li>\n\n\n\n
We use a for<\/code> loop to iterate through each number in the numbers<\/code> list. Inside the loop, we add each number to the total<\/code> variable.<\/li>\n\n\n\n
After looping through all the numbers in the list, we return the final total<\/code> value.<\/li>\n<\/ol>\n\n\n\n
Let’s try the function with some list:<\/p>\n\n\n\n
print("Sum of list from 1 to 5: " + str(sum_list([1, 2, 3, 4, 5])))\nprint("Sum of list from 5 to 10: " + str(sum_list([5, 6, 7, 8, 9, 10])))<\/pre><\/div>\n\n\n\n
The output is exactly as you might expect:<\/p>\n\n\n\n<\/figure>\n\n\n\n
<\/p>\n\n\n\n
Conclusion<\/h2>\n\n\n\n
In this post, you’ve learned about control structures (if and while) and how to define and user functions. These building blocks are vital for any program you write in the future. In the next lesson, you will learn about String and List. <\/p>\n\n\n\n
![\"Control](\"https:\/\/datmt.com\/wp-content\/uploads\/2023\/04\/image-2.png\")
<\/figure>\n\n\n\n![\"looping](\"https:\/\/datmt.com\/wp-content\/uploads\/2023\/04\/image-3.png\")
<\/figure>\n\n\n\n![\"While](\"https:\/\/datmt.com\/wp-content\/uploads\/2023\/04\/image-4.png\")
<\/figure>\n\n\n\n![\"Define](\"https:\/\/datmt.com\/wp-content\/uploads\/2023\/04\/image-5.png\")
<\/figure>\n\n\n\n![\"\"](\"https:\/\/datmt.com\/wp-content\/uploads\/2023\/04\/image.png\")
<\/figure>\n\n\n\n![\"Sumlist](\"https:\/\/datmt.com\/wp-content\/uploads\/2023\/04\/image-1.png\")
<\/figure>\n\n\n\n