AP Computer Science Principles: Midterms - Dolan

Output (Python)

print()

Output (AP Pseudocode)

DISPLAY

What does output mean in programming?

Showing information to the user (on the screen)

What data type is 5?

int (integer)

What data type is 3.14?

float

What data type is "Hello"?

str (string)

What data type is True?

bool (Boolean)

Boolean values in AP pseudocode

TRUE and FALSE

What is a variable?

A named container that stores a value that can change

Python variable assignment symbol

=

AP pseudocode assignment symbol

←

Python is case sensitive means

Age and age are different variables

Rules for variable names

Start with letter/_ ; use letters/numbers/_ ; no keywords ; meaningful names

What is a string?

Text (characters) inside quotes

What is string concatenation?

Joining strings together using +

How do you concatenate strings in Python?

Use +

How do you add a space when concatenating?

Put " " between words in the concatenation

Why can’t you add a number to a string with + in Python?

Different data types; must convert number to a string

Convert a number to a string in Python

str(number)

What does input() return by default in Python?

A string

How do you get user input in Python?

variable = input("prompt")

How do you get user input in AP pseudocode?

variable ← INPUT("prompt")

How do you convert input to an integer in Python?

int(input("prompt"))

What is a comment?

A note for humans that the computer ignores

Python comment symbol

#

Purpose of comments

Explain code and make it easier to understand/debug

What is debugging?

Finding and fixing errors in code

Syntax error

Code is written incorrectly; program won’t run

Runtime error

Program runs until it crashes while executing

Logic error

Program runs but gives the wrong output

Overflow error

Too-large number for the allowed storage/type (too much info)

Roundoff error

Small inaccuracies caused by rounding decimals

Common debugging strategy: tracing

Step through code line by line and track variable values

Common debugging strategy: test cases

Try different inputs to check behavior

Arithmetic operators

+, -, *, / (and others like %, **)

Addition operator

+

Subtraction operator

-

Multiplication operator

*

Division operator

/

Python division returns

A float (decimal), even if dividing integers

Exponent operator in Python

**

Exponent operator in AP pseudocode

^

What is modulus?

Remainder after division

Modulus operator in Python

%

Modulus operator in AP pseudocode

MOD

What is 10 % 2?

0

What is 7 % 3?

1

If the first number is smaller in modulus (3 % 5)

The answer is 3

How to check if a number is even

number % 2 == 0

How to check if a number is odd

number % 2 == 1

Order of operations acronym

PEMDAS

PEMDAS order

Parentheses, Exponents, Multiply/Divide/Modulus, Add/Subtract

What is 5 + 3 * 2?

11

What is (5 + 3) * 2?

16

Comparison operators produce

Boolean values (True/False)

Equality operator in Python

==

Equality operator in AP pseudocode

=

Not equal operator in Python

!=

Not equal operator in AP pseudocode

≠ or !=

Greater than operator

>

Less than operator

<

Greater than or equal operator

=

Less than or equal operator

Logical operators combine

Boolean expressions

AND means

True only if both conditions are true

OR means

True if at least one condition is true

NOT means

Flips the truth value (True becomes False, False becomes True)

Why parentheses matter in logic

They change the order and meaning of the condition

Using RANDOM(a, b) in AP pseudocode

Returns a random integer from a to b inclusive

Python equivalent of RANDOM(a, b)

random.randint(a, b)

What is an algorithm?

A step-by-step set of instructions to solve a problem

What is a control structure?

A structure that controls the flow of a program

Sequence

Running statements in order from top to bottom

Selection

Choosing between paths using IF/ELSE

Iteration

Repeating steps using loops

IF statement purpose

Runs code only when a condition is true

ELSE purpose

Runs code when the IF condition is false

FOR loop purpose

Repeats a set number of times

WHILE loop purpose

Repeats while a condition stays true

Infinite loop

A loop that never stops because the condition never becomes false

Nesting

Putting a loop inside an if, or an if inside a loop, etc.

Most common nesting pattern

Loop through items and use IF to check each one

What is a list?

An ordered collection of items stored in one variable

Python list indexing starts at

0

AP pseudocode list indexing starts at

1

How to create a list in Python

name = [items]

How to create a list in AP pseudocode

name ← [items]

How to get list length in Python

len(list)

How to get list length in AP pseudocode

length(list)

Last index in Python

len(list) - 1

Last index in AP pseudocode

length(list)

Traversing a list means

Going through each item in the list

Python for-each traversal

for item in list:

AP pseudocode for-each traversal

FOR EACH item IN list

Searching a list common pattern

Use a found flag (found = False/TRUE)

Found flag purpose

Tracks whether the target value was found in the list

Add to end of list in Python

list.append(value)

Add to end of list in AP pseudocode

APPEND(list, value)

Insert into a list in Python

list.insert(index, value)

Insert into a list in AP pseudocode

INSERT(list, position, value)