Recitations 4 & 6 (Intro to Computing, Test 1 Review)

Functions allow you to return ____value or _____of values.

a, a set

Returning vs Printing

Returning allows you to store a value for future use by setting a variable equal to the function call

• Ex: def multiplier(num1, num2):

product = num1 * num2

return product

my_product = multipler(5, 6)

What will my_product be equal to? 30

Printing simply displays the value to the console, which is useful for debugging but doesn’t allow you to store the value anywhere

• Ex: def multiplier(num1, num2):

product = num1 * num2

print(product)

my_product = multipler(5, 6)

What will my_product be equal to? None

Parts of a Function (Conceptual)

def function_name(parameter1, parameter2):

[lines of code]

return output_value

value = function_name(argument1, argument2)

print(value)

1| def multiplier(num1, num2):

2| product = num1 * num2

3| return product

4| print(multiplier(1, 2))

Label the parts of the function:

1| def multiplier(num1, num2):

2| product = num1 * num2

3| return product

4| print(multiplier(1, 2))

Line 1: Function Header (Function Name, Parameters: the variable placeholders defined in the function header)

Line 2-3: Function Body: Everything indented under the header

Line 4: Function Call (Arguments: values passed into the function when you call it)

Parameter vs Argument? In a variable analogy, what are parameters and what are arguments?

Parameters: the variable placeholders defined in the function header

• def multipler(num1, num2):

  
  

Arguments: values passed into the function when you call it

• print(multiplier(1, 2))

Variable Analogy

• Parameters: variable

• Arguments: values assigned to the variables

Do all functions need parameters?

no

Give the num2 parameter a default value of 0:

1| def multiplier(num1, num2):

2| product = num1 * num2

3| return product

4| print(multiplier(1))

1| def multiplier(num1, num2 = 0):

2| product = num1 * num2

3| return product

4| print(multiplier(1)

What is the output of this code?

1| def multiplier(num1, num2):

2| ——product = num1 * num2

3| ——return product

4| print(multiplier(1))

1| def multiplier(num1 = 2, num2):

2| ——product = num1 * num2

3| ——return product

4| print(multiplier(1))

(line 4) TypeError: multiplier() missing missing 1 required positional argument: 'num2'

(line 1) SyntaxError: parameter with a default value defined before parameter without a default value

What is the output of this code?

1| def multiplier(num1, num2 = 0):

2| product = num1 * num2

3| return product

4| print(multiplier(1))

0

Arguments are passed into parameters in the order that_______.

they are listed

T or F: Functions can call other functions.

True
Ex: def multiplier(num1, num2):

product = num1 * num2

return product

def powers(int1, int2, int3):

product = multiplier(int1, int2)

return product ** int3

print(powers(1,2,3))

_____let you run a piece of code repeatedly.

loops

2 Main Types of loops:

1)

2)

2 Main Types of loops:

1) For: specifies the number of times a statement will be executed; the variable used for looping increments in every loop; for n amount of times, perform some action

• for i in range(start, stop, step); for i in range(start, stop); for i in range(stop)

• for each character in a string, for each item in a list

2) While: executes a block of code while some condition is True and stops once the condition is False; while some condition is true, perform some action

Basic Structure of While Loops

While conditional:

[perform some task]

[modify/change conditional]

Infinite loop occur when…

There is no way for the conditional to be broken; conditional is never changes to False

• Remember to have code that beaks the loop eventually

How do infinite loops break your code?

the loop runs ‘forever’ and eventually raises a RunTime error; Note*: the error is not raised initially

range(start, stop, step)

• ______is the only required parameter.

• Start is _______ and stop is______.

• Stop is the only required parameter

• Start is inclusive and stop is exclusive. This means the range starts at the start input and ends before the end input.

  • Ex: for i in range(1, 5), print(i) —> 1,2,3,4

Range(start, stop, step)

• Default start =

• Default step =

• Default start = 0

• Default step = 1

Python is_______. This means that the first item in a string or the first value in a list is has the index____.

zero-indexed, 0

2 Main Types of For Loops

1) For a range of numbers: for i in range(start, stop, step):, for i in range(start, stop):, for i in range (stop)

• Ex: for i in range(len(“Aparna”)):

print(“Aparna”[i])

print(i)

2) For-Each Loops: Iterating through characters in string or items in a list a numbers

• Ex: count = 0

for char in “Aparna”:

print(char)

print(count)

What is the advantage of using a for loop with range() over a for-each loop?

A) There is no advantage

B) W/ range(), you iterate directly over the items

C) W/ range(), you know exactly how many iterations have a occured

D) W/ a for-each loop, you have to manually look up each item by index

C

True or False: Both for loops and while loops are generally interchangeable, but one might be more relevant/useful in a scenario than another

True

When might you use a while loop instead of a for loop?

A) Not all loops can be done relatively easily in a for loop.

B) All loops are interchangeable, there is no real advantage to using a while loop. It’s all personal preference.

C) While loops run a predetermined number of iterations, unlike a for loop.

D) The looping can be done with expressions that evaluate to True or False like conditionals.

AD

For which of the following problems should you use a for-loop?

• A) Repeating some action while some condition remains true

• B) Repeating some action for every letter in a string

• C) Repeating some action a pre-determined number of times

• D) Repeating some action until a certain goal is accomplished

• E) Repeating some action for every item in a list

BCE

• A —> While loop

• D —> Do-while loops (can be recreated with regular while loops in Python)

Allow you to run some code provided some condition is met.

conditional

portion of a program’s execution where a variable can be seen and accessed

scope