Python for Loop Introduction:
The for loop is a crucial control structure in Python that allows you to iterate over a sequence of elements or perform a set of actions a specified number of times. It is a fundamental construct in the language and is widely used for various purposes. In this article, we will explore the Python for loop in detail, understand its syntax and usage, and provide examples to demonstrate its versatility.
Syntax: The syntax of the for loop in Python is as follows:
for element in sequence:
# code block
The loop starts by iterating over each element in the sequence. The variable “element” takes the value of each item in the sequence, one at a time, until the loop completes. Inside the loop, you can perform any desired operations using the current value of “element”. The code block associated with the for loop is indented and executed for each iteration.
Iterating over a Sequence:
One common use of the for loop is to iterate over a sequence such as a list, tuple, string, or range. Let’s take a look at some examples:
Example 1: Iterating over a List
fruits = ['apple', 'banana', 'orange']
for fruit in fruits:
print(fruit)
Output:
apple
banana
orange
In this example, we have a list of fruits. The for loop iterates over each fruit in the list and prints it. The loop runs three times, once for each item in the list.
Example 2: Iterating over a String
message = "Hello, World!"
for char in message:
print(char)
Output:
H
e
l
l
o
,
W
o
r
l
d
!
Here, the for loop iterates over each character in the string “message” and prints it. The loop executes 13 times, once for each character in the string.
Example 3: Iterating over a Range
for num in range(1, 6):
print(num)
Output:
1
2
3
4
5
In this case, the for loop iterates over the range of numbers from 1 to 5 (excluding 6). The loop runs five times, and the variable “num” takes the value of each number in the range.
Controlling the Loop: Python provides additional control flow statements that can be used to modify the behavior of a for loop.
- break Statement: The break statement allows you to exit the loop prematurely. It is often used when a certain condition is met, and you want to stop the loop from further iterations.
Example:
fruits = ['apple', 'banana', 'orange']
for fruit in fruits:
if fruit == 'banana':
break
print(fruit)
Output:
apple
In this example, the loop is interrupted when the variable “fruit” becomes ‘banana’. Therefore, only the first fruit, ‘apple’, is printed.
- continue Statement: The continue statement allows you to skip the rest of the code block for the current iteration and move to the next iteration of the loop.
Example:
fruits = ['apple', 'banana', 'orange']
for fruit in fruits:
if fruit == 'banana':
continue
print(fruit)
Output:
apple
orange
Here, when the loop encounters ‘banana’, the continue statement is executed, and the code block is skipped for that iteration. As a result, ‘banana’ is not printed, and the loop moves on to the next item in the sequence.
Nested for Loops: Python allows you to nest one or more for loops inside another for loop. This is useful when you want to iterate over multiple sequences or perform operations on a multidimensional data structure.
Example: Nested for Loops
rows = range(1, 4)
columns = range(1, 3)
for row in rows:
for col in columns:
print(row, col)
Output:
1 1
1 2
2 1
2 2
3 1
3 2
In this example, we have two sequences: “rows” and “columns”. The outer for loop iterates over each row, and the inner for loop iterates over each column. The print statement displays the combination of row and column values.
The for loop is an essential construct in Python that allows you to iterate over sequences and perform repetitive tasks efficiently. It provides flexibility and control over the flow of your program. In this article, we covered the syntax of the for loop, examples of iterating over different types of sequences, and how to control the loop using break and continue statements. Understanding the for loop and its applications will greatly enhance your ability to write efficient and concise Python code.
