Python Basics

Question 1

Declarative Knowledge

Answer 1

A statement of fact

it does not tell you have to do stuff

Question 2

Imperative Knowledge

Answer 2

A recipe or “how-to”
(this tells you how to do something)
Also know as an algorithm

Question 3

What is a recipe?

Answer 3

1) A sequence of simple steps
2) Flow of control that specifies when each step is executed
3) Determining when to stop

Question 4

Syntax

Answer 4

Is passing of a sentence/string

Question 5

Static semantics

Answer 5

Is which syntactically valid strings have meaning

Question 6

Semantics

Answer 6

Is the meaning associated with syntactically correct string of symbols with no static semantic errors

Question 7

Program

Answer 7

Is a sequence of definitions and commands

• definitions are evaluated
• commands are executed

Question 8

Commands

Answer 8

Statements - instruct interpreter to do something

Question 9

Data objects

Answer 9

is what the program is manipulating

Question 10

Objects are

Answer 10

scalar (cannot be subdivided)

non-scalar (have internal structure that can be accessed)

Question 11

Object type

Answer 11

defines what the programs can do to them

Question 12

Scalar objects in Python

Answer 12

• Integers (int)
• Real numbers (float)
• Boolean (bool)
• Special (NoneType)

Question 13

cast

Answer 13

convert objects of one type to another

Question 14

combine objects and operators

Question 15

operator precedence without parentheses

Answer 15

**
*
/
\+ and -
execute left to right
parentheses always have top priority and get done first and will be evaluated inside out.

Question 16

assignment

Answer 16

equal sign is an assignment of a value to a variable name

• value stored in computer memory
• an assignment binds name to value
• retrieve value associated with name or variable by invoking the name

Question 17

Abstracting expressions

Answer 17

• give names to values of expressions
• reuse names instead of values
• easier to change code later

Question 18

Branching

Answer 18

• make a choice and do different things
• each statement gets executed once
• runs in constant time

Question 19

Variables (bindings)

Answer 19

• name (descriptive, meaningful, re-read code, no keywords)
• value (can be updated)
• right hand side -> VALUE
• left hand side -> VARIABLE

Question 20

String

Answer 20

• letters, special characters, spaces, digits
• enclosed in quotation marks or single quotes
• concatenate strings by using the + operator

Question 21

overloaded the + operator

Answer 21

is when using the + sign to concatenate two or more strings together

Question 22

for loops

Answer 22

• known number of iterations
• can end early via break
• use a counter
• can rewrite a for loop using while loop

Question 23

while loops

Answer 23

• unbound number of iterations
• can end early via break
• can use a counter, but must initialize before loop and increment inside loop
• may not be able to rewrite a while loop using a for loop

Question 24

compare/test object type

Answer 24

• type(object) returns the type of the object

- isinstance(object, type) testing if an object is of a certain type

Question 25

iterative code

Answer 25

• branching structures (conditionals) can jump to diff. pieces of code based on a test - programs are constant time
• looping structures (like while or for) let us repeat code until a condition is satisfied - programs take time depending on value of variables as well as length of program.

Question 26

Useful for a decrementing function

Answer 26

• maps set of program var into an integer
• when loop is entered, value is non-negative
• when value is <= 0, loop terminates and
• value is decreased every time through loop

Question 27

Need a loop variable

Answer 27

• initialize outside loop
• changes within loop
• test for termination depends on variable

Question 28

Guess-and-Check

Answer 28

• guess a value
• check if the solution is correct
• keep guessing until find solution or guessed all values
• the process is exhaustive enumeration