Iteration
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The document discusses different types of loops in Python including while loops, for loops, infinite loops, breaking and continuing loops. It provides examples of using while and for loops to iterate through lists and calculate values like sums, maximums, and minimums. Various loop patterns are demonstrated including counting, summing, and finding the max/min values from lists.
![ Eg:
names=['Ram','Shyam','Raj']
for x in names:
print("Happy New Year",x)
print('Done!')
List is an important data type.
Can take elements of different types.
Elements enclosed within square brackets.
Elements can be extracted using index.
If there are fixed set of numbers to iterate in a for loop, we can use range()](https://image.slidesharecdn.com/iteration-200909073946/85/Iteration-11-320.jpg)
![ range(start, end, steps)
Start: starting values
End: ending values but excluding ending value
Steps: increment/ decrement [default value is 1]
1. for i in range(5):
print(i,end='t')
2. for i in range(5,0,-1):
print(i,end='t')
3. for i in range(0,10,2):
print(i,end='t')](https://image.slidesharecdn.com/iteration-200909073946/85/Iteration-12-320.jpg)
![ while and for loop used to go through a list of items and check max or min data values.
1. Initialize one/more variables before loop starts.
2. Perform computation
3. Look result
Counting and Summing Loops:
count=0
for i in [4,-2,41,34,25]:
count=count+1 #COUNT
print("Count=",count)
total=0
for i in [4,-2,41,34,25]:
total=total+I #SUMMATION
print("Total=",total)
Loop Patterns](https://image.slidesharecdn.com/iteration-200909073946/85/Iteration-13-320.jpg)
![big=None
print("Before Loop:",big)
for x in [12,0,21,-3]:
if big is None or x>big: #MAXIMUM
big=x
print("Itearation Variable:",x,'Big',big)
print("Biggest:",big)
small=None
print("Before Loop:",small)
for x in [12,0,21,-3]:
if small is None or x<small: #MINIMUM
small=x
print("Iteration Variable:",x,'Small',small)
print("Smallest:",small)](https://image.slidesharecdn.com/iteration-200909073946/85/Iteration-14-320.jpg)
Iteration
- 2. while statements Infinite loop and break Finishing iterations with continue Definite loops using for Loop Pattern Counting and Summing loops Maximum and Minimum loops Iteration
- 3. The while Statement Syntax: while condition: Statement 1 Statement 2 ….. Statement N Statements after while while: keyword conditions will be evaluated and leads True or False if True Statements will be executed else exits.
- 4. Eg: 1. n=1 while n<=5: print(n) n=n+1 print("Over") 2. n=5 while n>=0: print(n) n=n-1 print("Exit")
- 5. Loop execute infinite number of times. Eg: n=1 while True: print(n) n=n+1 Above program, loop condition is True, so it will never exits. If we want to come out from the loop, we use break. Eg: n=1 while True: print(n) n=n+1 break Infinite Loops, break and continue
- 6. Eg: 1. while True: x=int(input("Enter a Number:")) if x>=0: print("You have entered a positive number. The number is:",x) else: print("You have entered a negative number") 2. while True: x=int(input("Enter a Number:")) if x>=0: print("You have entered a positive number. The number is:",x) else: print("You have entered a negative number") break
- 8. Move to next iterations , use continue statement. Eg: sum=0 count=0 while True: x= int (input ("Enter a Number:")) if x%2==0: continue else: sum=sum+x count=count+1 if count==5: break print("Sum=",sum) continue statement
- 9. Definite Loops using for
- 10. Syntax of for loop: for var in list/sequence: Statement 1 Statement 2 ….. Statement N Statements after for loop for and in are keywords list/ sequence is a set of elements on which the loop iterates statements constitutes the body of loop
- 11. Eg: names=['Ram','Shyam','Raj'] for x in names: print("Happy New Year",x) print('Done!') List is an important data type. Can take elements of different types. Elements enclosed within square brackets. Elements can be extracted using index. If there are fixed set of numbers to iterate in a for loop, we can use range()
- 12. range(start, end, steps) Start: starting values End: ending values but excluding ending value Steps: increment/ decrement [default value is 1] 1. for i in range(5): print(i,end='t') 2. for i in range(5,0,-1): print(i,end='t') 3. for i in range(0,10,2): print(i,end='t')
- 13. while and for loop used to go through a list of items and check max or min data values. 1. Initialize one/more variables before loop starts. 2. Perform computation 3. Look result Counting and Summing Loops: count=0 for i in [4,-2,41,34,25]: count=count+1 #COUNT print("Count=",count) total=0 for i in [4,-2,41,34,25]: total=total+I #SUMMATION print("Total=",total) Loop Patterns
- 14. big=None print("Before Loop:",big) for x in [12,0,21,-3]: if big is None or x>big: #MAXIMUM big=x print("Itearation Variable:",x,'Big',big) print("Biggest:",big) small=None print("Before Loop:",small) for x in [12,0,21,-3]: if small is None or x<small: #MINIMUM small=x print("Iteration Variable:",x,'Small',small) print("Smallest:",small)