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Python language gives us a powerful looping structure known as for loop, through which we could execute statements in a loop(again and again) while iterating over a sequence of values. These sequence of values could be given to us by -

• The range() function, or
• Collection data types of Python such as -list, tuple, dictionary or set, which are used to store a sequence/collection of values.

• The range() function


We could use the for loop to execute the statements in a loop, while iterating over a sequence of values given by the range() function. The range() function returns a sequence of numbers, starting at a specified value(default is 0), each value is incremented by a specified value(default is 1) and ending at a specified value.

Syntax of range() function -

range(start, end, increment)



Where,
• The start is the starting integer value of the sequence and it is optional with default value 0.
• The end is the last integer value(minus 1) of the sequence and it is not optional.
• The increment is the integer number for incrementation, and it is optional with default value 1.







Using for loop with range() function


Let us see how to use the for loop with the range() function.



# Python for loop with range() function



# This gives us a sequence of values starting from 2 to 4 and incrementing by 1
x = range(2,5)


print('First for loop :')


# Using for loop is used to print the sequence of values
for i in x:
    print(i)

	
	
	
	
# This gives us a sequence of values starting from 0 to 5 and incrementing by 1
x = range(6)


print('Second for loop :')


# For loop is used to print Hello for each number in the sequence of values
for n in x:
    print('Hello')
    print(n)




Output




First for loop:
2
3
4
Second for loop:
Hello
0
Hello
1
Hello
2
Hello
3
Hello
4
Hello
5








• Using for loop to iterate over a collection


Collection data types of Python such as -list, tuple, dictionary or set are used to store a sequence/collection of values. We could use the for loop to execute the statements in a loop, while iterating over a sequence of values stored in a collection.








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• for loop iterating over a list


The elements of a list collection are declared within in square brackets i.e [ ]



#Python - for loop iterating over elements stored in a list

#A list
a_list = [1, 2, 3, 4, 5] 

#for loop iterating over list
for x in a_list:
	print("x =", x)    





Output




x = 1
x = 2
x = 3
x = 4
x = 5








• for loop iterating over a tuple


The elements of a tuplex collection are declared within in curly braces i.e { }



#Python - for loop iterating over elements stored in a tuple

#A tuple
a_list = (1, 2, 3, 4, 5)

#for loop iterating over list
for x in a_list:
	print("x =", x)    





Output




x = 1
x = 2
x = 3
x = 4
x = 5








• for loop iterating over a set


The elements of a set collection are declared within in curly braces i.e { }



#Python - for loop iterating over elements stored in a set

#A set
a_set = {1, 2, 3, 4, 5}

#for loop iterating over a set
for x in a_set:
	print("x =", x)    
   





Output




x = 1
x = 2
x = 3
x = 4
x = 5








• for loop iterating over a dictionary


The elements of a dictionary collection are declared within in curly braces i.e { }. Each value in a dictionary collection is stored in a pair of key and value, where, using the value of a key, we can access its associated value stored in a dictionary.

The for loop, when iterating over a dictionary collection data type returns the key, using which we could access its associated value stored in the dictionary.



#Python - for loop iterating over elements stored in a list

#A dictionary
a_dictionary = {
                        "one":"1",
			"two":"2",
			"three":"3",
			"four":"4",
			"five":"5"
}

#for loop iterating over pairs of key and value stored in a dictionary
for x in a_dictionary:
	print(x, a_dictionary[x])





Output




one 1
two 2
three 3
four 4
five 5







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