What is Loop ?

C Language Loops | C++ Language Loops - In general, statements are executed sequentially: The first statement in a function is executed first, followed by the second, and so on. There may be a situation when you need to execute a block of code several number of times. Programming languages provide various control structures that allow for more complicated execution paths.

Python has two primitive loop commands:

1. for loop
2. while loop

Python For Loops :

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 language, and works more like an iterator method as found in other object-oriented programming languages. With the for loop we can execute a set of statements, once for each item in a list, tuple, set etc.

Example :

ourlist=["ayan","apu","dev","symul"] for x in ourlist: print(x) #Print each members in a member list print("\n--new line--") for x in "TECHBAZ.ORG": print(x) #Loop through the letters in the word "TECHBAZ.ORG" input()

Output :

for loop with Statements :

With the break statement we can stop the loop before it has looped through all the items and the continue statement we can stop the current iteration of the loop, and continue with the next. For Example :

Example 1 :

ourlist=["ayan","apu","dev","symul"] for x in ourlist: if x == "apu": print(x) break #The break Statement input()

Output 1 :

Example 2 :

ourlist = ["ayan", "apu", "dev", "symul"] for x in ourlist: if x == "apu": continue #The continue Statement print(x) input()

Output 2 :

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.

Example 1 :

for x in range(10): print(x) input()

Output 1 :

Note : That range(10) is not the values of 0 to 10, but the values 0 to 9.

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, 8), which means values from 2 to 8 (but not including 8).

Example 2 :

for x in range(2,8): print(x) input()

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, 40, 3)

Example 3 :

for x in range(2,40,3): print(x) input()

Example 3 :

Else in For Loop :

The else keyword in a for loop specifies a block of code to be executed when the loop is finished.

Example :

for x in range(8): print(x) else: print("\n loop finished!") input()

Example :

Nested for loops :

A nested loop is a loop inside a loop. The "inner loop" will be executed one time for each iteration of the "outer loop".

Example :

n = 10 for x in range (0,n) : print("\n") for y in range (x + 1) : print(n-y,end=" ") #if you want to print stars, use ' print(end="*") ' input()

Output :

Note : Python’s print() function comes with a parameter called ‘end’. By default, the value of this parameter is ‘\n’, i.e. the new line character. You can end a print statement with any character/string using this parameter.