Lecture 7 - Bisection Search

Question 1

Why None and False are printed to the console as a result from calling the div_by() function?

Answer 1

function does not return any value

When div_by() function is called with arguments 10 and 3, Python evaluates the expression 3%10 == 0, which is False, resulting in the block inside the else statement being executed.

Then, Python will execute the print(div_by(10,3)) line. Since the function does not return any value, the function call div_by(10,3) does not return any value. Therefore, when this is printed to the console, it yields the None type, which is the absence of any value.

Question 2

What is a function in Python?

Answer 2

A function in Python is a reusable block of code that performs a specific task. Functions are important because they allow programmers to generalise code, reducing redundancy and making programs more modular and easier to maintain.

Question 3

What is the difference between formal parameters and actual parameters in a function?

Answer 3

Formal parameters are the names used in the function definition to represent the inputs the function expects. Actual parameters (or arguments) are the specific values passed to the function when it is called; these values are then bound to the formal parameters.

Question 4

What happens during a function call?

Answer 4

During a function call, the actual parameters are evaluated and bound to the formal parameters. The point of execution moves to the function body, which is executed until a return statement is encountered or the end of the body is reached. Finally, a value is returned to the calling code.

Question 5

What are keyword arguments?

Answer 5

Keyword arguments bind formals to actuals using the name of the formal parameter. Unlike positional arguments, which rely on order, keyword arguments explicitly identify which formal parameter receives which actual parameter.

Question 6

Give an example of using keyword arguments.

Answer 6

print_name(last_name='Smith', first_name='John')

Question 7

How do default parameter values work in Python functions?

Answer 7

Default parameter values allow a function to be called with fewer arguments than specified, in which case the default values are used for the missing parameters. They are useful for providing sensible defaults, reducing the burden on the caller, and making function calls more flexible.

Question 8

How can a Python function accept a variable number of arguments?

Answer 8

A Python function can accept a variable number of positional arguments using the unpacking operator * in the parameter list. The *args syntax gathers all positional arguments into a tuple named args, which can then be iterated over within the function.

Question 9

What is scoping in Python?

Answer 9

Scoping in Python refers to the region of a program where a name (variable) is visible and can be accessed. When a function is called, a new symbol table (stack frame) is created to track names defined within the function.

Question 10

What is a function specification?

Answer 10

A function specification is a contract between the implementer of a function and its clients, defining what the function does and how it should be used. It includes assumptions about the input parameters and guarantees about the function’s behaviour and output.

Question 11

What are the two main components of a function specification?

Answer 11

The two main components of a function specification are:
* Assumptions about the input parameters
* Guarantees about the function’s behaviour and output.

Question 12

Explain the concept of decomposition in programming.

Answer 12

Decomposition is breaking a program into self-contained, reusable parts, like functions, to create structure. It helps manage complexity and improve code organization.

Question 13

What is abstraction in programming?

Answer 13

Abstraction hides the inner details of a piece of code so it can be used as a black box. It is essential in managing complexity and promoting code reuse.

Question 14

What is a docstring in Python?

Answer 14

A docstring is a string literal that occurs as the first statement in a function definition. It is used to document the function’s purpose, arguments, and return value.

Question 15

How can a docstring be accessed?

Answer 15

A docstring can be accessed using the help() function or IDE tools.

Question 16

What is a formal parameter?

Answer 16

A formal parameter is a variable name used in a function definition to represent an input value.

Question 17

What is an actual parameter (argument)?

Answer 17

An actual parameter (argument) is the value passed to a function when it is called, which is then bound to the corresponding formal parameter.

Question 18

What is a positional argument?

Answer 18

A positional argument is an argument passed to a function based on its position in the function call, matching the order of formal parameters.

Question 19

What is a keyword argument?

Answer 19

A keyword argument is an argument passed to a function using the name of the formal parameter, allowing arguments to be specified out of order and improving code readability.

Question 20

What is a default parameter value?

Answer 20

A default parameter value is a value assigned to a formal parameter in a function definition, which is used if the corresponding argument is not provided in the function call.

Question 21

What is the unpacking operator (*) in Python?

Answer 21

The unpacking operator (*) is used in function definitions to accept a variable number of positional arguments, which are collected into a tuple.

Question 22

What is a scope in programming?

Answer 22

A scope is the region of a program where a name (variable) is visible and can be accessed.

Question 23

What is a symbol table (stack frame)?

Answer 23

A symbol table (stack frame) is a data structure used to store the names and bindings of variables within a particular scope, such as a function.

Question 24

What is static/lexical scoping?

Answer 24

Static/Lexical scoping is a scoping rule in which the scope of a name is determined by its position in the program text.

Question 25

What is debugging?

Answer 25

Debugging is the process of finding and fixing errors in a program.

Question 26

What is lambda abstraction?

Answer 26

Lambda abstraction is the ability for programmers to write code that accesses not specific objects, but instead whatever objects the caller of the function chooses to use as actual parameters.

Question 27

What is the primary benefit of using functions in Python programming?

Answer 27

Code reusability and organization.

Question 28

Explain the difference between built-in functions and user-defined functions.

Answer 28

Built-in functions are provided by Python, while user-defined functions are created by the programmer. ## Footnote Examples of built-in functions include `print()` and `len()`. An example of a user-defined function is one created using the `def` keyword.

Question 29

Describe the purpose of the `def` keyword in Python.

Answer 29

To define a new function.

Question 30

What is the difference between a parameter and an argument in the context of Python functions?

Answer 30

A parameter is a variable in the function definition, while an argument is the actual value passed to the function. ## Footnote Example: In `def func(param):`, `param` is a parameter; in `func(arg)`, `arg` is an argument.

Question 31

How does the `return` statement work in a Python function?

Answer 31

It exits the function and optionally passes back a value. If no return statement is present, the function returns None.

Question 32

Explain the purpose of a docstring and how to access it.

Answer 32

A docstring provides documentation for a function, and it can be accessed using the `.__doc__` attribute.

Question 33

What is the scope of a variable defined inside a function?

Answer 33

Local to the function.

Question 34

How do you define a function with a default parameter value?

Answer 34

By assigning a value in the function definition. ## Footnote Example: `def func(param=default_value):`.

Question 35

What are named (keyword) arguments?

Answer 35

Arguments passed to a function by explicitly specifying the parameter name. ## Footnote They are useful for improving code readability and allowing flexibility in argument order.

Question 36

Describe what anonymous functions are in Python.

Answer 36

Functions defined using the `lambda` keyword, typically for short, throwaway functions.

Question 37

``` def print_name(first_name, last_name, reverse): if reverse: print(last_name + ', ' + first_name) else: print(first_name, last_name) ``` What is the output from the following function call? `>>> print_name('Olga', last_name = 'Puchmajerova', False)`

Answer 37

It would be an error message since it is not legal to follow a keyword argument with a non-keyword argument.