Python - for Loop

<Nested if while >

Till now, we have learned and executed sequential statements. Sometimes we want to do the same task a fixed number of times. This is done by using Looping statements.

Loop control statement is also known as repetition statements or iteration statements.

Python supports the following Loop control flow statements.

for loop
while loop

The for loop

A for loop usually iterates over sequential data types such as string, list, tuple, set, or dictionary.

Syntax of Python for loop

for variable_name in sequence_type:
      Statement(s)

The for loop executes a set of statements once for each item in the sequence type.

Flow Chart

Python for Loop Example

The following example uses the for loop to display the items from the Agelist.

For example:
>> Agelist=[20,30,40,50]
>> for a in Agelist:
...      print(a)
...

When you execute the above program, you will get the following output.

...
20
30
40
50
>>

Sometimes we want to display the index of each member in the list. We can do that by using enumerate() function.

>> Agelist=[20,30,40,50]
>> for In_Agelist in enumerate(Agelist):
...      print(In_Agelist)
...

While executing the above code, you will get the following output.

...
(0, 20)
(1, 30)
(2, 40)
(3, 50)
>>

The range() Function

In for loop, the range() function is used in the place of sequence to specify the initial, final, and incremental values for iteration.
The range() function generates the lists that start from start to till stop-1.
The syntax of the range() function is.


 range([start],stop,[step])

The start is referred to as the initial value. If the start argument is not mentioned, then the sequence starts from zero by default.
The stop is referred to as the final value. But not including the number itself.
The step is referred to as the increment value.
Here both start and step arguments are optional.
All arguments value should always be an integer.

Example with range() Function

Following is an example to demonstrate the range() function.

print("To speify the stop only argument:")
for i in range(5):
    print("The value of i is: ",i)
print("To specify both start and stop arguments:")
for i in range(4,10):
    print("The value of i is: ",i)
print("To specify all three arguments:")
for i in range(1,8,2):
    print("The value of i is: ",i)