What’s interesting to do with booleans, and expressions that return a boolean in particular, is that we can make decisions and take different roads depending on their True
or False
value.
In Python we do so using the if
statement:
condition = True
if condition == True:
# do something
When the condition test resolves to True
, like in the above case, its block gets executed.
What is a block? A block is that part that is indented one level (4 spaces usually) on the right:
condition = True
if condition == True:
print("The condition")
print("was true")
The block can be formed by a single line, or multiple lines as well, and it ends when you move back to the previous indentation level:
condition = True
if condition == True:
print("The condition")
print("was true")
print("Outside of the if")
In combination with if
you can have an else
block, that’s executed if the condition test of if
results to False
:
condition = True
if condition == True:
print("The condition")
print("was True")
else:
print("The condition")
print("was False")
And you can have different linked if
checks with elif
, that’s executed if the previous check was False
:
condition = True
name = "Roger"
if condition == True:
print("The condition")
print("was True")
elif name == "Roger":
print("Hello Roger")
else:
print("The condition")
print("was False")
The second block in this case is executed if condition
is False
, and the name
variable value is “Roger”.
In a if
statement you can have just one if
and else
checks, but multiple series of elif
checks:
condition = True
name = "Roger"
if condition == True:
print("The condition")
print("was True")
elif name == "Roger":
print("Hello Roger")
elif name == "Syd":
print("Hello Syd")
elif name == "Flavio":
print("Hello Flavio")
else:
print("The condition")
print("was False")
if
and else
can also be used in an inline format, which lets us return a value or another based on a condition.
Example:
a = 2
result = 2 if a == 0 else 3
print(result) # 3
More python tutorials:
- Introduction to Python
- Installing Python 3 on macOS
- Running Python programs
- Python 2 vs Python 3
- The basics of working with Python
- Python Data Types
- Python Operators
- Python Strings
- Python Booleans
- Python Numbers
- Python, Accepting Input
- Python Control Statements
- Python Lists
- Python Tuples
- Python Sets
- Python Dictionaries
- Python Functions
- Python Objects
- Python Loops
- Python Modules
- Python Classes
- The Python Standard Library
- Debugging Python
- Python variables scope
- Python, accept arguments from command line
- Python Recursion
- Python Nested Functions
- Python Lambda Functions
- Python Closures
- Python Virtual Environments
- Use a GoPro as a remote webcam using Python
- Python, how to create a list from a string
- Python Decorators
- Python Docstrings
- Python Introspection
- Python Annotations
- Python, how to list files and folders in a directory
- Python, how to check if a number is odd or even
- Python, how to get the details of a file
- Python, how to check if a file or directory exists
- Python Exceptions