status: #doc #unfinished 
Tags: : #python #programming 
links:[[python]] 
Date: 2023-05-01
___
# [loop](https://www.w3schools.com/python/python_while_loops.asp) in python

Python has two primitive loop commands:

-   while loops
-   for loops

## The while Loop
it run if condition is true  
```python
i = 1
while i < 6:
  print(i)
  i += 1
```
 here it run till i = 6 so if i is less then  6 condition is true else it  become false
 --->output
 ```sh
1
2
3
4
5
```

## Python For Loops

A `for` loop is used for iterating over a sequence (that is either a list, a tuple, a dictionary, a set, or a string) its not like other programming language

- Print each fruit in a fruit list:
```python
fruits = ["apple", "banana", "cherry"]  
for x in fruits:  
  print(x)
```
and here is the [[`in` usage  in python|in]] usage

### [range()](https://www.w3schools.com/python/ref_func_range.asp) loop specific number of times

To loop through a set of code a specified number of times, start from 0 to N

```python
for x in range(6):  
  print(x)
```

>[!Note]
>range(6) is not the values of 0 to 6, but the values 0 to 5.
>

### Else in For Loop

The `else` keyword in a `for` loop specifies a block of code to be executed when the loop is finished:

- Print all numbers from 0 to 5, and print a message when the loop has ended:
```python
for x in range(6):  
  print(x)  
else:  
  print("Finally finished!")
```

>[!note]
>The `else` block will NOT be executed if the loop is stopped by a `break` statement.

## break statement

With the break statement we can stop the loop even if the condition is true:
- Exit the loop when i is 3:
```python
i = 1  
while i < 6:  
  print(i)  
  if i == 3:  
    break  
  i += 1
```

- how it work
![[Pasted image 20230501160831.png|300]]

## continue statement

With the continue statement we can stop the current iteration of the loop, and continue with the next:

- Do not print banana:
```python
fruits = ["apple", "banana", "cherry"]  
for x in fruits:  
  if x == "banana":  
    continue  
  print(x)
```

--->output
```sh
apple  
cherry
```
how it work
![[Pasted image 20230501160908.png|300]]

---
## The pass Statement
`for` loops cannot be empty, but if you for some reason have a `for` loop with no content, put in the `pass` statement to avoid getting an error.

```python
for x in [0, 1, 2]:  
  pass
```
# References

https://www.w3schools.com/python/python_while_loops.asp
https://www.w3schools.com/python/python_for_loops.asp
https://www.programiz.com/python-programming/break-continue