Loop ... Else Clause, Partial Functions & Type Hints

Loop ... Else Clause

In Python, the else clause in a loop is executed when the loop terminates normally (when a break statement is not executed). This is in contrast to the try and except statements, where the else block is executed when no exception is raised.

For... else

In Python, the for statement is used to iterate over a sequence (such as a list, tuple, or string) or other iterable object. The else clause in a for loop is optional and is executed only if the loop completed normally (that is, if the loop was not interrupted by a break statement).

• The else clause would execute if our iteration or loop executes normally without breaking

• The else clause will also execute if the loop is empty

items = [1 , 2]

for i in items:
    print("number", i)
    
    # if we break the loop at some point the else would not work
    if(i == 2):
        break
else:
    print("The loop is either empty or did not run normally")

While... else

In Python, the while loop executes a block of code repeatedly as long as a certain condition is true. The else clause in a while loop in Python is optional and is executed only when the condition in the while loop becomes False. It is not executed if the loop is terminated by a break statement.

items = [1, 2, 3, 4, 5]
count = 0

while count < len(items):
    count = count + 1
    if(count == 4):
        break
    print(count)
else:
    print("The loop is either empty or did not run normally")

The else clause in a loop can be a useful way to add some additional logic that should be executed only if the loop completes normally. However, it's important to note that the else clause is not the same as the else clause in a try and except block. The else clause in a try and except block is executed when no exception is raised, whereas the else clause in a loop is executed when the loop terminates normally.