Python While Loop
while is simplest loop in python programming that is depending of expression which are provide by program. result of expression in boolean form. if that result are not false then that will executes loop statement.
There syntax as follows.
while expressionCondition: #statements #statements-N
index=10 #expression (index<=15) while index<=15: #statements print(index) index+=1
10 11 12 13 14 15
When expression is false, then terminates execution of while loop. that is a very simple example. we can used any kind of expression and condition. let take another example to print list elements using while loop.
listData=[1,2,4,5,6] #simple list terminate=len(listData) #get size of list index=0 while index<terminate: #expression print(listData[index]) #display list data index+=1 #modified index
1 2 4 5 6
We can print list element using of "for" loop of very efficient manner. but that is an also alternate to display list element.
Nested while loop in python
Nested is a way to organize one conditional block inside another conditional block in similar type. in similar way to define one loop inside another (while loop) that is called nested of while loop.
while expression1: #statements while expression2: #statements while expressionN: #statements
#Nested while loop example listData=[100,[1,2,3],[9,7,8,11]] i=0 j=0 innerLength=0 outerLength=len(listData) #outer while loop while i<outerLength: j=0 if(type(listData[i])==list) : innerLength=len(listData[i]) else: print("list[",i,"]",listData[i]) #not list innerLength=0 #inner while loop while j<innerLength: print("list[",i,"][",j,"]",listData[i][j]) j+=1 i+=1
list[ 0 ] 100 list[ 1 ][ 0 ] 1 list[ 1 ][ 1 ] 2 list[ 1 ][ 2 ] 3 list[ 2 ][ 0 ] 9 list[ 2 ][ 1 ] 7 list[ 2 ][ 2 ] 8 list[ 2 ][ 3 ] 11
in similar way we can use any number of nested while loops in programs.
Brake are used to terminate loop execution within the specified condition.
point=10 while True: if(point<=-1 or point>=20): break #condition to terminate loop print(point) point+=3 print("After terminate loop :",point)
10 13 16 19 After terminate loop : 22
This statement are manage execution flow of loop. this statement are only used within the loop.
point=1 while point<10: point+=1 if(point>=3 and point<=7): continue print(point) print("After terminate loop :",point)
2 8 9 10 After terminate loop : 10