Python programming language provides the following types of loops to handle looping requirements. Python provides three ways for executing the loops. While all the ways provide similar basic functionality, they differ in their syntax and condition checking time.
Python For loop
A for loop is used for iterating over a sequence (that is either a list, a tuple, a dictionary, a set, or a string).
This is less like the for keyword in other programming languages, and works more like an iterator method as found in other object-orientated programming languages.
With the for loop we can execute a set of statements, once for each item in a list, tuple, set etc.
fruits = ["apple", "banana", "cherry"] for x in fruits: print(x)
The for loop does not require an indexing variable to set beforehand.
Looping Through a String
Even strings are iterable objects, they contain a sequence of characters:
fruits = ["apple", "banana", "cherry"] for x in fruits: if x == "banana": break print(x)
The continue Statement
With the continue statement we can stop the current iteration of the loop, and continue with the next:
fruits = ["apple", "banana", "cherry"] for x in fruits: if x == "banana": continue print(x)
The range() Function
To loop through a set of code a specified number of times, we can use the range() function,
The range() function returns a sequence of numbers, starting from 0 by default, and increments by 1 (by default), and ends at a specified number.
for x in range(7): print(x)
Note that range(6) is not the values of 0 to 6, but the values 0 to 6.
The range() function defaults to 0 as a starting value, however it is possible to specify the starting value by adding a parameter: range(2, 6), which means values from 2 to 6 (but not including 6):
for x in range(2, 6): print(x)
The range() function defaults to increment the sequence by 1, however, it is possible to specify the increment value by adding a third parameter: range(2, 30, 3):
for x in range(2, 30, 3): print(x)
Else in For Loop
else keyword in a
for loop specifies a block of code to be executed when the loop is finished:
for x in range(6): print(x) else: print("Finally finished!")
else block will NOT be executed if the loop is stopped by a
A nested loop is a loop inside a loop.
The “inner loop” will be executed one time for each iteration of the “outer loop”:
adj = ["red", "big", "tasty"] fruits = ["apple", "banana", "cherry"] for x in adj: for y in fruits: print(x, y)
Python while loop
The while loop in Python is used to iterate over a block of code as long as the test expression (condition) is true.
We generally use this loop when we don’t know the number of times to iterate beforehand.
Syntax of while Loop in Python
while expression: Body
Let’s see it with an example
i=0 while i < 5: print(i) i=i+1
Here, the loop will run until the condition gets false and it will exit the loop.
#Output 0 1 2 3 4
While loop with else
Same as with for loops, while loops can also have an optional
else part is executed if the condition in the while loop evaluates to
The while loop can be terminated with a break statement. In such cases, the
else part is ignored. Hence, a while loop’s
else part runs if no break occurs and the condition is false.
Here is an example to illustrate this
counter = 0 while counter < 3: print("Inside loop") counter = counter + 1 else: print("Inside else")
Inside loop Inside loop Inside loop Inside else
Here, we use a counter variable to print the string Inside loop three times.
On the fourth iteration, the condition in
False. Hence, the
else part is executed.
Hence we studied different types of loops in python with there definition and implementation along with it.
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