List Loops

List using For Loop

• The for loop in python is used to iterate over a sequence (list, tuple, string) or other iterable objects
• Iterating over a sequence is called traversal
• Loop continues until we reach the last item in the sequence
• The body of the for loop is separated from the rest of the code using indentation

Syntax

for val in sequence

for val in range(start,stop,step)

Example

Accessing the values in the list

list1 = [10,20,40,30,50,60]
for val in list1:
	print(val)

Output,

10
20
40
30
50
60

Accessing index and values  using range( )

list1 = [10,20,40,30,50,60]
for i in range(len(list1)):
	print("value at {0} is {1}".format(i,list1[i]))

Output,

value at 0 is 10
value at 1 is 20
value at 2 is 40
value at 3 is 30
value at 4 is 50
value at 5 is 60

Accessing index and values  using range( )

list1 = [10,20,40,30,50,60]
for i in range(1,len(list1),2):
	print("value at {0} is {1}".format(i,list1[i]))

Output

value at 1 is 20
value at 3 is 30
value at 5 is 60

Accessing element using index

subject=["python","maths","chemistry"]
for i in range(len(subject)):
	print(subject[i])

Output

python
maths
chemistry

List using While Loop

While loop in python is used to iterate over a block of code as long as the test expression (condition) is true

When the condition is tested and the result is false, the loop body will be skipped and the first statement after the while loop will be executed

Syntax

while(condition):
      body of while

Example

Sum of Elements in the list

list1=[10,20,30,40,50]
sum =0
i=0
while(i<len(list1)):
	sum=sum+list1[i]
	i=i+1
print("Sum of Elements in list:",sum)

Output

Sum of Elements in list: 150

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