Algorithms For Dummies

 Getting Started

Notice that the condition uses the relational equality operator, 

==

, and not the 

assignment operator, 

=

. A common mistake that developers make is to use the 

assignment operator rather than the equality operator. Using the assignment 

operator in place of the equality operator will cause your code to malfunction.

The condition always ends with a colon (:). If you don’t provide a colon, Python 

doesn’t know that the condition has ended and will continue to look for additional 

conditions on which to base its decision. After the colon comes any tasks you want 

Python to perform.

You may need to perform multiple tasks using a single if statement. The 

elif

 

clause makes it possible to add an additional condition and associated tasks. A 

clause is an addendum to a previous condition, which is an 

if

 statement in this 

case. The 

elif

 clause always provides a condition, just as the 

if

 statement does, 

and it has its own associated set of tasks to perform.

Sometimes you need to do something no matter what the condition might be. In 

this case, you add the 

else

 clause. The 

else

 clause tells Python to do something 

in particular when the conditions of the 

if

 statement aren’t met.

Notice how indenting is becoming more important as the functions become more 

complex. The function contains an 

if

 statement. The 

if

 statement contains just 

one 

print()

 statement. The 

else

 clause contains two 

print()

 statements.

To see this function in action, type TestValue(1) and press Enter. You see the out-

put from the 

else

 clause. Type TestValue(5) and press Enter. The output now 

reflects the 

if

 statement output. Type TestValue(6) and press Enter. The output 

now shows the results of the 

elif

 clause. The result is that this function is more 

flexible than previous functions in the chapter because it can make decisions.