Branching Basics and Multi-Branch Statements in Python
Branching is a fundamental concept in programming that allows your code to make decisions and execute different blocks of code based on certain conditions. In Python, we achieve branching using various statements, with the most common being:
if
statementelse
statementelif
statement (else if)
1. if
Statement
The if
statement is the core of branching. It checks a condition and executes a block of code indented below it only if the condition evaluates to True
.
Syntax:
if condition:
# Code to execute if condition is True
Example:
age = 25
if age >= 18:
print("You are eligible to vote.")
else:
print("You are not eligible to vote.")
2. else
Statement
The else
statement provides an alternative block of code to execute if the condition in the if
statement is False
. It's optional and can be used alone after an if
statement.
Syntax:
if condition:
# Code to execute if condition is True
else:
# Code to execute if condition is False
Example (from above):
age = 25
if age >= 18:
print("You are eligible to vote.")
else:
print("You are not eligible to vote.")
3. elif
Statement (else if)
The elif
statement (short for "else if") allows you to check multiple conditions sequentially. It's used after an if
statement and before an optional else
statement. The code block associated with the first elif
whose condition evaluates to True
will be executed. Subsequent elif
statements and the final else
block (if present) will be skipped.
Syntax:
if condition1:
# Code to execute if condition1 is True
elif condition2:
# Code to execute if condition1 is False and condition2 is True
# ... more elif statements
else:
# Code to execute if all conditions are False (optional)
Example:
grade = 85
if grade >= 90:
print("Excellent!")
elif grade >= 80:
print("Very Good!")
elif grade >= 70:
print("Good!")
else:
print("Needs Improvement.")
Tips for Using Branching Statements:
- Indentation is crucial in Python. The code block associated with an
if
,elif
, orelse
statement needs to be indented at the same level (usually with 4 spaces). - Make sure your conditions are well-defined and cover all possible scenarios to avoid unexpected behavior.
- Use clear and meaningful variable names to improve code readability.
- Consider nesting
if
statements within otherif
orelif
blocks for more complex decision-making logic.
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