CPIT 110 - (Chapter 2/Elementary Programming)

Tracing a program

Helps you to understand how programs work

If an item is a number,

The number is automatically converted to a string for displaying

Variable

Represents a value stored in the computer’s memory

Every variable has a

Name and value

Every value has a

Data type

Data type

Used to specify what type of the value are being used, such as integers or strings

Python provides

Basic (built-in) data types for integers, real numbers, string, and Boolean types

Input function

Used to ask the user to input a value, and then return the value entered as a string

Eval

Used to evaluate and convert the passed value (string) to a numeric value

If the user enters something other than a number,

The program will terminate with a runtime error

\

Used at the end of a line to tell the interpreter that the statement is continued on the next line

The three steps a program run on:

Input (input from the user),

Process (produce results using the input),

Output (displays the results)

Identifier

The names that identify the elements such as variables and functions in a program

Rule of an indentifier

Sequence of characters that consists of letters, digits, and underscores (_), and cannot be a keyword

Keyword

Reserved words, have special meanings in Python

Import

A keyword which tells the Python interpreter to import a module to the program

Variables

Used to reference (represent) values that may be changed in the program

Assignment statement

The statement for assigning a value to a variable

=

Used as the assignment operator

Expression

Represents a computation involving values, variables, and operators that, taken together, evaluate to a value

A variable can also be used

In both sides of the = operator.

Scope of a variable

The part of the program where the variable can be referenced (used)

A variable must be assigned a value before it can

Be used in an expression

Simultaneous assignment

It tells Python to evaluate all the expressions on the right and assign them to the corresponding variable on the left simultaneously

Swapping variable values

A common operation in programming and simultaneous assignment is very useful to perform this operation

A named constant is an identifier that represents

A permanent value

The value of a variable can change

During execution of a program

A named constant

Represents a permanent data that never changes

Data

What the information stored in a computer is generally referred to

Two types of numeric data

Integers and real numbers

Integer types (int for short)

Are for representing whole numbers

Real types

Representing numbers with a fractional part

Real numbers

Represented as floating-point (or float) values

Literal

A constant value that appears directly in a program (such as 1.0 or 1)

+

Addition

-

Subtraction

*

Multiplication

/

Float division

//

Integer division

**

Exponentiation

%

Remainder

The +, -, and * operators are straightforward, but note that the
+ and - operators can be both

Unary and binary

Unary operator

Only one operand

Binary operator

Has two operands

% operator (known as remainder)

Yields the remainder after division

Left-side operand

The dividend

Right-side operand

The divisor

Calculations involving floating-point numbers are approximated

Because these numbers are not stored with complete accuracy

Overflow

When a variable is assigned a value that is too large (in size) to
be stored

Underflow

When a floating-point number is too small (for example, too
close to zero) to be stored

There are no spaces in

The augmented assignment operators

The augmented assignment operator

Performed last after all the other operators in the expression are evaluated

Type conversion

The process of changing a value from one data type to another

If you would like to change the variable being converted by the
functions int and round,

Reset the variable after invoking the function

The int function can also be used to convert

An integer string into an integer

You can use the str(value) function to convert

The numeric value to a string