PyForLoopstest.txt

Loops

Sometimes, you need to perform code on each item in a list. This is called
 iteration, and it can be accomplished with a while loop and a counter variable.
For example:
words = ["hello", "world", "spam", "eggs", "জমজ"]
counter = 0
max_index = len(words) - 1

while counter <= max_index:
    word = words[counter]
    print(word + "!")
    counter = counter + 1



Result:
>>>
hello!
world!
spam!
eggs!
'জমজ!
>>>


The example above iterates through all items in the list, accesses them using
 their indices, and prints them with exclamation marks.

for Loop

Iterating through a list using a while loop requires quite a lot of code, so Python provides the for loop as a shortcut that accomplishes the same thing.
The same code from the previous example can be written with a for loop, as follows:
words = ["hello", "world", "spam", "eggs"]
for word in words:
  print(word + "!")

and 

letters = ['a', 'b', 'c']
  
for l in letters:
   print(l)

Result:
>>>
hello!
world!
spam!
eggs!

and

a
b
c
>>>

The for loop in Python is like the foreach loop in other languages.

for Loops

The for loop is commonly used to repeat some code a certain number of times.
 This is done by combining for loops with range objects.


for i in range(5):
  print("hello!")


and

for i in range(5):

  print("hello!")


for i in range(5):
 
  print (i)


for i in range(5):

  print ("i")


Result:
>>>
hello!
hello!
hello!
hello!
hello!


and

hello!
hello!
hello!
hello!
hello!
0
1
2
3
4
i
i
i
i
i
>>>


to create a for loop that prints only the even values in the range:

  
for i in range(0, 20, 2):
  print(i)

result:
>>>
0
2
4
6
8
10
12
14
16
18



You don't need to call list on the range object when it is used in a for loop,
 because it isn't being indexed, so a list isn't required.



for i in range(10):
  if not i % 2 == 0:
    print(i+1)


and

while False:
  print("Looping...")


Result

>>>
2
4
6
8
10

and

No output
>>>

print the first element of the list, if it contains even number of elements.

list = [1, 2, 3, 4]
if len(list) % 2 == 0:
   print(list[0])


and

letters = ['x', 'y', 'z']
letters.insert(1, 'w')
print(letters[2])

and

list = [1, 2, 3]
  
for var in list:
  print(var)    
>>>

1

and

y

and

1
2
3

>>>