"break", "continue", and "pass" Statements
Sometimes it is necessary to exit a loop abruptly when a certain condition is met. The "break" statement is sometimes useful for such an application. Consider this code:
strval='forever' for letter in strval: if letter =='e': break print('The letter e has been found')
In this case, the break statement terminates the loop if the character e is found in the strval string.
On the other hand, encountering a given condition within a loop may require skipping over a set of commands and effectively "fast-forward" to the next iteration. The "continue" statement is useful for these applications.
Finally, the "pass" statement within a loop is a null statement that does nothing. It is sometimes useful when placed in a program where code is intended but has not yet been written. Read this page and practice the examples.
The break Statement
The break statement is used to break out of a loop statement i.e. stop the execution of a looping statement, even if the loop condition has not become False or the sequence
of items has not been completely iterated over. An important note is that if you break out of a
for or while loop, any corresponding loop else block is not executed.
Example (save as
break.py):
while True: s = input('Enter something : ') if s == 'quit': break print('Length of the string is', len(s)) print('Done')Output:
$ python break.py Enter something : Programming is fun Length of the string is 18 Enter something : When the work is done Length of the string is 21 Enter something : if you wanna make your work also fun: Length of the string is 37 Enter something : use Python! Length of the string is 11 Enter something : quit Done
How It Works
In this program, we repeatedly take the user's input and print the length of each input each time. We are providing a special condition to stop the program by checking if the user input is
'quit'.
We stop the program by breaking out of the loop and reach the end of the program. The length of the input string can be found out using the built-in
len function. Remember that the
break statement can be used with the for loop as well. Swaroop's Poetic Python
The input I have used here is a mini poem I have written:
Programming is fun When the work is done if you wanna make your work also fun: use Python!
The 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. Example (save as
continue.py):
while True: s = input('Enter something : ') if s == 'quit': break if len(s) < 3: print('Too small') continue print('Input is of sufficient length') # Do other kinds of processing here...Output:
$ python continue.py Enter something : a Too small Enter something : 12 Too small Enter something : abc Input is of sufficient length Enter something : quit
How It Works
In this program, we accept input from the user, but we process the input string only if it is at least 3 characters long. So, we use the built-in
len function to get the
length and if the length is less than 3, we skip the rest of the statements in the block by using the continue statement. Otherwise, the rest of the statements in the loop are executed, doing any kind of processing
we want to do here. Note that the continue statement works with the for loop as well.
Summary
We have seen how to use the three control flow statements -if, while and for along with their associated break and continue statements. These are some of the most commonly used parts of Python and hence, becoming comfortable with them is essential. Next, we will see how to create and use functions.
Source: https://python.swaroopch.com/control_flow.html
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