Lecture 8 - Functions: environments, scope, functions as objects Flashcards
What is the purpose of a function’s docstring?
It serves as documentation, explaining what the function does, its parameters, and what it returns.
A docstring is considered a ‘contract’ as it outlines the guarantees made by the function writer regarding its behavior with specific inputs.
What happens when a return statement is executed in a Python function?
The function immediately stops, and the specified value is passed back to the part of the code that called the function.
If no explicit return statement exists, the function implicitly returns None.
Differentiate between formal parameters and actual arguments.
Formal parameters are the variables in the function definition; actual arguments are the values passed during a function call.
Example: In def greet(name):, ‘name’ is a formal parameter. In greet(‘Alice’), ‘Alice’ is the actual argument.
What is local scope in Python?
It refers to the visibility of variables within the function where they are defined.
A local variable is created when the function is called and ceases to exist when the function finishes executing.
Can a function access a variable defined in the global scope?
Yes, if a local variable with the same name is not defined within the function.
What does it mean for functions to be ‘first-class objects’ in Python?
It means functions can be treated like any other data type.
Examples include assigning a function to a variable or passing it as an argument to another function.
Describe what happens when a function call is made in terms of execution flow.
Python pauses the current code execution, creates a new local environment for the function, and the arguments are bound to the function’s parameters.
These environments are separate, meaning variables in one do not affect those in another unless specified.
What is the purpose of the global keyword in Python?
It declares that a variable name refers to a variable in the global scope, allowing modification of global variables.
Extensive use of global variables can complicate code and lead to unexpected side effects.
What is a lambda expression?
A concise way to create anonymous functions in Python, in the form lambda arguments: expression.
Example: lambda x: x * 2 defines a function that takes x and returns its value multiplied by 2.
What is a Function Definition?
The process of creating a reusable block of code with a name, parameters, and a body containing statements to be executed. The def keyword is used.
What does Function Call (Invocation) refer to?
The act of executing a defined function by using its name followed by parentheses, possibly including arguments.
What are Parameters in the context of functions?
Variables declared in the function definition that act as placeholders for the values the function will receive.
Define Arguments in relation to functions.
The values passed to a function during a function call, assigned to the corresponding formal parameters.
What is a Return Statement?
A statement within a function that specifies the value to be passed back to the caller.
What happens during an Implicit Return?
If a function reaches the end of its body without an explicit return statement, it implicitly returns None.
What is a Docstring?
A multiline string literal used to document a function, describing its purpose, arguments, and return value.
What does it mean that a Function is treated as an Object in Python?
Functions can be assigned to variables, passed as arguments, and returned as values from other functions.
Define Scope in programming.
The region of a program where a particular name (variable, function) is accessible.
What is Global Scope?
Variables defined outside of any function that are potentially accessible from anywhere in the program.
What is Local Scope?
Variables defined inside a function that are only accessible within that function.
What are Environments (Frames) in the context of function calls?
Each function call creates a new local environment containing local variables and parameters of that specific call.
What is Name Binding?
The association of a name (variable) with an object (value, function).
What is the purpose of the global Keyword?
Indicates that a name refers to a global variable, allowing modification of the global variable from within the function.
What does the nonlocal Keyword do?
Indicates that a name refers to a variable in the nearest enclosing function’s scope.
What is Higher-Order Programming?
A programming style that treats functions as data, allowing them to be passed as arguments or returned as values.
What is a Lambda Expression?
A way to create small, anonymous functions using the lambda keyword.
What is Abstraction?
The process of hiding complex implementation details and exposing only essential information to the user
Functions serve as a form of abstraction.
What is an Argument in programming?
The value passed to a function when it is called, also referred to as the actual parameter
Arguments are used to provide input values to functions.
What is the Body of a function?
The block of indented statements that are executed when the function is called
The body contains the logic that defines what the function does.
What is a Call Stack?
A data structure that keeps track of the active function calls in a program
When a function is called, a new frame is added to the stack; when it returns, the frame is removed.
What is a Closure?
A function object that remembers values in enclosing scopes even if they are no longer present in the environment
Closures are related to the concept of scope.
What is Decomposition?
Breaking down a large, complex problem into smaller, more manageable subproblems, often implemented as separate functions
This approach enhances problem-solving and code organization.
What is a First-Class Object?
An entity that can be passed as an argument, returned from a function, assigned to a variable, and treated like any other value
Functions in Python are considered first-class objects.
What is a Formal Parameter?
A variable name declared in the function definition that will receive a value when the function is called
Formal parameters act as placeholders for the arguments.
What is a Function?
A named sequence of statements that performs a specific task, taking inputs (arguments) and producing outputs (return values)
Functions are fundamental building blocks in programming.
What is a Higher-Order Function?
A function that takes one or more functions as arguments or returns a function as its result
Higher-order functions facilitate functional programming techniques.
What is the Lifetime of a variable?
The period during which a variable exists in the computer’s memory
Local variables typically exist only during the execution of the function in which they are defined.
What is Modularity?
The organisation of code into independent and interchangeable modules (like functions), each representing a self-contained piece of functionality
Modularity promotes code reusability and easier maintenance.
What is a NameError?
A Python exception that occurs when you try to use a variable or function name that has not been defined in the current scope
This error indicates an attempt to access an undefined identifier.
What is a Namespace?
A system that provides unique names for objects, preventing name collisions
Different scopes can have their own namespaces.
What is a Parameter?
A variable in the definition of a function, acting as a placeholder for an argument
Parameters are specified in the function definition and receive values when the function is invoked.
What is Recursion?
A programming technique where a function calls itself within its own definition
Recursion is a powerful method for solving problems that can be broken down into smaller instances of the same problem.
What is a Return Value?
The value that a function sends back to the caller using the return statement
Return values are used to output results from functions.
What is a Side Effect?
An action that a function performs that is not explicitly part of its return value, such as printing to the console
Side effects can alter the state of the program or its environment.
What is a Stack Frame?
Another term for the environment created when a function is called, containing local variables and other information relevant to that specific invocation
Each function call creates a new stack frame in the call stack.
