for Loop in Python

A `for` loop is used for iterating over a sequence (that is either a list, a tuple, a dictionary, a set, or a string).

With the for loop we can execute a set of statements, once for each item in a list, tuple, set etc.

#### Syntax:

```
for var in sequence:
statement(s)  must be indented
```

Here, `var` is the variable that takes the value of the item inside the sequence on each iteration.

Loop continues until we reach the last item in the sequence.

Example 1:

Print each fruit in a fruit list:
```fruits = ["apple", "banana", "mango"]
for x in fruits:
print(x)```
OUTPUT
```apple
banana
mango```

Example 2:

Program to find the sum of all numbers stored in a list
```# List of numbers
numbers = [1,2,3,10,20,34]

# variable to store the sum
sum = 0

# iterate over the list
for var in numbers:
sum = sum+var

# Output: The sum is 70
print("The sum is", sum)```
OUTPUT
`The sum is 70`

Looping through a String

Even strings are iterable objects, they contain a sequence of characters:

Example 3:

Loop through the letters in the word "prowess":
```for x in "prowess":
print(x)```
OUTPUT
```p
r
o
w
e
s
s```

The range() function :

We can generate a sequence of numbers using `range()` function.

#### Syntax :

`1. range(stop)` always starts from 0 to stop-1.

`range(10)` will will generate numbers from 0 to 9 (10 numbers).

```>>> print(range(10))
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>>```

`2. range(start, stop, step)` We can also define the start, stop and step size.Step size defaults to 1 if not provided.

`range(1,10)` will will generate numbers from 1 to 9 (10 numbers).

```>>> print(range(1,10))
[1, 2, 3, 4, 5, 6, 7, 8, 9]  step is 1

>>> print(range(1,10,2))
[1, 3, 5, 7, 9]  step is 2

>>> print(range(10,1,-1))  step is -1
[10, 9, 8, 7, 6, 5, 4, 3, 2]  #generate the reverse series```

We can use the range() function in for loops to iterate through a sequence of numbers.

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

0
1
2
3
4```

`range()` function can be combined with the `len()` function to iterate though a sequence using indexing.

``` Program to iterate through a list using indexing

fruit = ['apple', 'banana', 'mango']

# iterate over the list using index
for i in range(len(fruit)):
print("I like", fruit[i])```
OUTPUT
```I like apple
I like banana
I like mango```

for loop with else :

In python, a for loop can have an optional else block as well. The `else` block is executed if the items in the sequence used in for loop exhausts.

```for x in range(6):
print(x)
else:
print("Finally finished!")```
OUTPUT
```0
1
2
3
4
5
Finally finished!```

Nested Loops

A nested loop is a loop inside a loop.

The "inner loop" will be executed one time for each iteration of the "outer loop":

Print each adjective for every fruit:

```adj = ["red", "big", "tasty"]
fruits = ["apple", "banana", "cherry"]

for y in fruits:
print(x, y)```
OUTPUT
```red apple
red banana
red cherry
big apple
big banana
big cherry
tasty apple
tasty banana
tasty cherry```

Next topic is break, continue and pass statements

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