Common Structure of Python Compound Statements

In Python, a compound statement is a group of statements that performs a specific task. It consists of one or more clauses, each of which is made up of a header and a suite. The header is a single line that specifies the conditions under which the suite is executed, while the suite is a group of statements that are executed as a unit.

There are several types of compound statements in Python, including if statements, for loops, and while loops. In this article, we will focus on the common structure of these statements and provide examples of how they work.

If statements

An if statement is used to execute a suite of statements if a certain condition is true. The general syntax of an if statement is as follows:

If the condition is true, the suite of statements will be executed. If the condition is false, the suite will be skipped.

Here is an example of an if statement in Python:

Output:

Explanation:

The output of this program will be "x is greater than 5" because the condition (x > 5) is true.

You can also use an if statement with an else clause, which specifies a suite of statements to be executed if the condition is false. The syntax for an if-else statement is as follows:

Here is an example of an if-else statement in Python:

Output:

Explanation:

The output of this program will be "x is not greater than 5" because the condition (x > 5) is false.

You can also use an if statement with multiple conditions and multiple else clauses using the elif keyword. The syntax for this is as follows:

In this case, the program will first check condition 1. If it is true, suite1 will be executed. If condition1 is false, the program will move on to condition2 and execute suite2 if it is true. If none of the conditions are true, the program will execute suite3.

Here is an example of an if statement with multiple conditions and else clauses:

Output:

Explanation:

The output of this program will be "x is not greater than 5 or 3" because none of the conditions are true.

For loops

A for loop is used to iterate over a sequence of elements, such as a list or a string. The general syntax of a for loop is as follows:

for variable in sequence:

The variable is a placeholder for the current element in the sequence, and the suite is executed for each element in the sequence.

Here is an example of a for loop in Python:

Output:

Explanation:

This program will output the numbers 0 through 4, one per line because range(5) generates a sequence of numbers from 0 to 4.

You can also use the for loop to iterate over a list or a string. For example:

Output:

Explanation:

T his program will output the elements of the list one per line: "apple", "banana", "cherry".

You can use the range function to specify a range of elements to iterate over. For example:

Output:

Explanation:

This program will output the numbers 2, 3, and 4, because range(2, 5) generates a sequence of numbers from 2 to 4.

You can also specify a step size using the range function. For example:

Output:

Explanation:

This program will output the odd numbers from 1 to 9, because range(1, 10, 2) generates a sequence of numbers from 1 to 9 with a step size of 2.

While loops

A while loop is used to execute a suite of statements repeatedly as long as a certain condition is true. The general syntax of a while loop is as follows:

The suite will be executed repeatedly as long as the condition is true.

Here is an example of a while loop in Python:

Output:

Explanation:

This program will output the numbers 5, 4, 3, 2, and 1, because the condition (x > 0) is true as long as x is greater than 0, and the value of x is decremented by 1 each time through the loop.

It is important to include a statement in the suite that eventually makes the condition false, or the loop will execute indefinitely and create an infinite loop.

In summary, the common structure of Python compound statements includes if statements, for loops, and while loops. These statements allow you to execute a suite of statements conditionally or repeatedly based on specified conditions. They are an important part of Python programming and are widely used in many applications.