Counting Loop

Code Example1

count = 0
print ('before',count)
for thing in [45, 45,67,23,1,23,78,90]:
    count = count + 1
    print (count , thing)
print('After' ,count)

we set the variable = 0 then add then each time the code run just to count how many time it run

Output

before 0
1 45
2 45
3 67
4 23
5 1
6 23
7 78
8 90
After 8

Example 2

rock = 0
print ('Before',rock)
for thing in [56,78,2,90,45]:
    rock = thing +rock
    print (rock,thing)
print ('After',rock)

we sum the thing and rock each time it run

Output

Before 0
56 56
134 78
136 2
226 90
271 45
After 271

Finding the Average in the loop

Code Example 3

count = 0
sum = 0
print ('Before',count ,sum)
for value in [7,89,4,67,25,33]:
    count = count +1
    sum = sum + value
    print (count,sum,value)
print('After',count,sum,sum/count)

Output

Before 0 0
1 7 7
2 96 89
3 100 4
4 167 67
5 192 25
6 225 33
After 6 225 37.5

Filtering in the loop

Code Example 4

print('Before')
for value in [45,14,7,23,87]:
    if value > 20:
        print('large number:',value)
print ('After')

It will check and print out if the value is larger than 20 and go back and check again till the end of the value

Output

Before
large number: 45
large number: 23
large number: 87
After

Search using Boolean Variable

• Boolean has only Two value , True and False

code Example 5

found = False
print('Before',found)
for value in [56,34,67,8,12,3,0]:
    if value == 8:
        found = True
    print (found,value)
print('After',found)

Output

Before False
False 56
False 34
False 67
True 8
True 12
True 3
True 0
After True

As you can see that it turns True when it found 8 and then even if the conditional is not true it still print out True(maybe i will find in exercise)

• How to find the smallest value?

  ## Code Example 6

    largest_so_far = -1
    print ('Before',largest_so_far)
    for the_num in [45,2,67,8,12,44]:
        if the_num > largest_so_far:
            largest_so_far = the_num
        print(largest_so_far,the_num)
    print('After', largest_so_far)
  

  ### Output

    Before -1
    45 45
    45 2
    67 67
    67 8
    67 12
    67 44
    After 67
  

• Answer

  Just change the > to <

    smallest_so_far = -1
    print ('Before',smallest_so_far)
    for the_num in [45,2,67,8,12,44]:
        if the_num < smallest_so_far:
            smallest_so_far = the_num
        print(smallest_so_far,the_num)
    print('After', smallest_so_far)
  

  ### Output

    Before -1
    -1 45
    -1 2
    -1 67
    -1 8
    -1 12
    -1 44
    After -1
      
  

  if we make the first smallest_so_far to bigger number

    smallest_so_far = 100
    print ('Before',smallest_so_far)
    for the_num in [45,2,67,8,12,44]:
        if the_num < smallest_so_far:
            smallest_so_far = the_num
        print(smallest_so_far,the_num)
    print('After', smallest_so_far)
  

    Before 100
    45 45
    2 2
    2 67
    2 8
    2 12
    2 44
    After 2
  

None

• None is a constant that has only one value is None

Code Example 7

smallest = None
print ('Before')
for value in [45,2,67,9,23]:
    if smallest is None:
        smallest = value
    elif value < smallest:
        smallest = value
    print (smallest,value)
print ('After',smallest)

Output

Before
45 45
2 2
2 67
2 9
2 23
After 2

None is means nothing

is means ==

is not means False

Question

• Which of these evaluates to False?

  0 == 0.0

  0 is 0.0

  0 is not 0.0

  0 = 0.0

• Answer

  0 is 0.0