121 lines
2.6 KiB
Markdown
121 lines
2.6 KiB
Markdown
status: #doc #unfinished
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Tags: : #python #programming
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links:[[python]]
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Date: 2023-05-01
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___
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# [loop](https://www.w3schools.com/python/python_while_loops.asp) in python
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Python has two primitive loop commands:
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- while loops
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- for loops
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## The while Loop
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it run if condition is true
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```python
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i = 1
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while i < 6:
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print(i)
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i += 1
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```
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here it run till i = 6 so if i is less then 6 condition is true else it become false
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--->output
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```sh
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1
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2
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3
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4
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5
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```
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## Python For Loops
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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
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- Print each fruit in a fruit list:
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```python
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fruits = ["apple", "banana", "cherry"]
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for x in fruits:
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print(x)
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```
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and here is the [[`in` usage in python|in]] usage
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### [range()](https://www.w3schools.com/python/ref_func_range.asp) loop specific number of times
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To loop through a set of code a specified number of times, start from 0 to N
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```python
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for x in range(6):
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print(x)
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```
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>[!Note]
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>range(6) is not the values of 0 to 6, but the values 0 to 5.
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>
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### Else in For Loop
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The `else` keyword in a `for` loop specifies a block of code to be executed when the loop is finished:
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- Print all numbers from 0 to 5, and print a message when the loop has ended:
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```python
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for x in range(6):
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print(x)
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else:
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print("Finally finished!")
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```
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>[!note]
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>The `else` block will NOT be executed if the loop is stopped by a `break` statement.
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## break statement
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With the break statement we can stop the loop even if the condition is true:
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- Exit the loop when i is 3:
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```python
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i = 1
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while i < 6:
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print(i)
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if i == 3:
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break
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i += 1
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```
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- how it work
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![[Pasted image 20230501160831.png|300]]
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## continue statement
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With the continue statement we can stop the current iteration of the loop, and continue with the next:
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- Do not print banana:
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```python
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fruits = ["apple", "banana", "cherry"]
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for x in fruits:
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if x == "banana":
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continue
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print(x)
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```
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--->output
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```sh
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apple
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cherry
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```
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how it work
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![[Pasted image 20230501160908.png|300]]
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---
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## The pass Statement
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`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.
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```python
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for x in [0, 1, 2]:
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pass
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```
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# References
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https://www.w3schools.com/python/python_while_loops.asp
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https://www.w3schools.com/python/python_for_loops.asp
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https://www.programiz.com/python-programming/break-continue
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