Python loop statements
A loop statement used to execute a statement or group of statements multiple times based on condition.
Python has following types of loop statements :
And except it Python has following loop control statement :
Python While loop
It will repeat the statement till the condition is true, and tests the condition before executing it.
while condition: statement1 statement2
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Python For Loop
The for..in statement is another looping statement which iterates over a sequence
of objects i.e. it will go each time through an object.
To implement For loop, you need three things :
- Test of condition
for initialization in range(start,end,increment): statement1 statement2
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1 2 3 4 The for loop is over
Benefits of For loop
- Number of times loop should run is known.
- Use of a counter
- Can use a False condition to terminate the loop.
Nested Loop in Python
Nested loop means loop in side a loop.One loop is called as inner loop and one is called as outer.
Example of while nested loops
[pastacode lang=”python” manual=”%23!%2Fusr%2Fbin%2Fpython%0A%0Ax%20%3D%202%0Awhile(x%20%3C%2050)%3A%0A%20%20%20y%20%3D%202%0A%20%20%20while(y%20%3C%3D%20(x%2Fy))%3A%0A%20%20%20%20%20%20if%20not(x%25y)%3A%20break%0A%20%20%20%20%20%20y%20%3D%20y%20%2B%201%0A%20%20%20if%20(y%20%3E%20x%2Fy)%20%3A%20print%20x%2C%20%22%20%20%20is%20%20prime%22%0A%20%20%20x%20%3D%20x%20%2B%201%0A%0Aprint%20%22You%20did%20it!%22″ message=”Finding prime numbers using nested loop” highlight=”” provider=”manual”/]
2 is prime 3 is prime 5 is prime 7 is prime 11 is prime 13 is prime 17 is prime 19 is prime 23 is prime 29 is prime 31 is prime 37 is prime 41 is prime 43 is prime 47 is prime You did it!
Which loop you should use?
- For Loop : It is a pretest loop and that is used in expressions for initializing, testing and updating a counter. It is very convenient to use the for loop where number of times the loop should execute is known.
- While Loop : While loop is ideal for situations where you don’t want loop to iterate if condition is false. Best example of it is checking health in a game until someone dies.
Loop control statement : Break
The break statement is used to break out of a loop statement ie. it will stop the execution of looping statement, even if condition has not become false.
Let’s see one best use of Break statement through a program. We are going to write a program that will take string as input from the user and returns length of the string. If user wants to quit then simple user will give input as quit, and program will stop the execution.
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Enter something : How are you? Length of the string is 12 Enter something : I am good. How are you? Length of the string is 23 Enter something : quit See you again
Python Continue Statement
The continue statement is used to tell Python to skip the rest of the statements in the current loop block and to continue to the next iteration of the loop.
Python Pass Statement
Pass is a null statement. The difference between a comment and
pass statement is that, while the interpreter ignores a comment entirely,
pass is not ignored.
However, nothing happens when pass is executed. It results into no operation.
Hope You enjoyed the tutorial. Comment for further questions?