0Class 12 Python – Functions: Scope, Parameter Passing, and Return Values
1. Functions in Python
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A function is a block of reusable code that performs a specific task.
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Functions help in modular programming, making code organized, readable, and maintainable.
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Functions are defined using the
defkeyword.
2. Scope of Variables
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Scope refers to the region of the program where a variable is accessible.
a) Local Scope
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A local variable is defined inside a function.
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Accessible only within that function.
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Disappears once the function ends.
b) Global Scope
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A global variable is defined outside all functions.
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Accessible throughout the program, including inside functions.
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Can be used to share data across multiple functions.
Key Points
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If a local variable and a global variable have the same name, the local variable takes precedence inside the function.
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Use global variables carefully to avoid unexpected results.
3. Parameter Passing
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Parameters are inputs given to a function so it can perform its task.
a) Types of Parameters
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Positional Parameters: Values are passed in order.
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Keyword Parameters: Values are passed using parameter names.
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Default Parameters: A default value is used if no argument is provided.
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Variable-length Parameters: Function can accept any number of arguments.
Key Points
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Parameters allow functions to be flexible and reusable.
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Proper use of parameters avoids hard-coding values.
4. Return Values
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Functions can return a value to the part of the program that called them.
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If no value is returned, the function performs the task but gives nothing back.
Key Points
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The return value can be stored in a variable for later use.
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Functions can return multiple values simultaneously.
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Using return values allows modular, testable, and maintainable code.
5. Summary Table
| Concept | Description |
|---|---|
| Local Variable | Defined inside a function; accessible only within it |
| Global Variable | Defined outside functions; accessible everywhere |
| Parameter | Input value provided to a function |
| Return Value | Value a function gives back to the caller |
| Flexible Functions | Use positional, keyword, default, or variable-length parameters |
6. Key Tips
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Always use descriptive names for parameters and variables.
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Keep global variables minimal to avoid confusion.
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Use return values to make functions powerful and reusable.
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Parameter passing allows customized behavior without changing function code.
