Python Chapter 2
Math expressions
Performs a calculation and give a value 12 + 2
Comments
Short notes placed in different parts of a program, explaining how those parts of the program work. Ignored by the python interpreter, they are intended for any person reading a program's code, not the computer
Parallelograms
Used as INPUT symbols and OUTPUT symbols. They represent steps in which the program reads input or display output.
Rectangles
Used as PROCESSING symbols. They represent steps in which the program performs some process on data, such as a mathematical calculation
String literal
When a string appears in the actual code of a program, it is a string literal. Must be enclosed in quote marks
References
When a variable represents a value in the computer's memory, we say that the variable references the value
Calling
When programmers execute a function, they say that they are calling the function
Assignment statement
You use an assignment statement to create a variable and make it reference a piece of data. Ex: age = 25
line continuation
\
named constant
a name that represents a value that cannot be changed during the program's execution
A magic number is
a number that is mathematically undefined
numeric literal
a number that is written into a program's code
escape character
a special character that is preceded with a backslash \ \n causes output to be advanced to the next line \t causes output ot skip over the next horizontal tab position \' causes a single quote to be printed \'' causes a double quote mark to be printed \\ causes a backslash character to be printed
format specifier
a string that contains special characters specifying how the numeric value should be formatted '.2f'
A(n) --- is a set of well-defined logical steps that must be taken to perform a task
algorithm
mixed-type expression
an expression that uses operands of different data types
magic number
an unexplained value that appears in a program's code
An ___ makes a variable reference a value in the computer's memory
assignment statement
Variable naming rules
cannot contain spaces cannot use python's key words uppercase and lowercase matters etc...
short notes placed in different parts of a program explaining how those parts of the program work
comments
Data types
different types of numbers are stored and manipulated in different ways, python uses data types to categorize values in memory
A string literal in Python must be enclosed in
either single-quotes or double quotes
new line character
end=' '
Invalid
example: the variable that is receiving the assignment must appear on the left side of the =operator invalid: 72 = amount
If you print a variable that has not been assigned a value, the number 0 will be displayed.
false
Programmers must be careful not to make syntax errors when writing pseudocode programs.
false
Variable names can have spaces in them.
false
Suppose the following statement is in a program: price = 99.0. After this statement executes, the price variable will reference a value of this data type.
float
This built-in function can be used to convert an int value to a float.
float( )
A --- is a diagram that graphically depicts the steps that take place in a program
flowchart
how do you suppress the print function's ending newline?
if you do not want the print function to start a new line of output when it finishes displaying its output, you can pass the special argument end = ' ' to the function
This built-in function can be used to read input that has been typed on the keyboard.
input( )
#
marks the beginning of a comment in Python
a ___is a name that represents a value that does not change during the program's exceptional execution
named constant
what are three advantages of using named constants
named constants make programs more self-explanatory widespread changes can easily be made to the program they help to prevent the typographical errors that are common when using magic numbers
In the expression 12 + 7, the values on the right and left of the + symbol are called
operands
An informal language that has no syntax rules, and is not meant to be compiled or executed is called: pseudocode
pseudocode
%
remainder operator. also known as the modulus operator
no space between lines
sep='' can add a symbol in the middle of the quotes
A --- is a single function that the program must perform in order to satisfy the customer
software requirement
str
storing string in memory
A --- is a sequence of characters that is used as data
string
//
this operator performs integer division
In Python the first character of a variable name cannot be a number.
true
In a math expression, multiplication and division takes place before addition and subtraction.
true
A --- is any hypothetical person that is using a program and providing input for it
user
A --- is a storage location in memory that is represented by a name
variable
Assignment operator
variable = expression. the equal sign is known as the assignment operator
float
when a real number is stored in memory ex: 1.5, 3.14159, 5.0
Garbage collection
when a value in memory is no longer referenced by a variable, the python interpreter automatically removes it from memory through a process known as garbage collection
int
when an integer is stored in memory it is classified as an int ex: 7, 124, -9
17 = x
will cause an error in Python, must be in x = 17 order
how can you change the character that is automatically displayed between multiple items that are passed to the print function?
you can pass the argument sep= to the print function, specifying the desired character
Exception
An unexpected error that occurs while a program is running, causing the program to halt if the error is not properly dealt with
Input
Any data that the program receives while it is running. Like data that is typed on a keyboard. Once input is received, the results of the process are then sent out of the program as output
User
Any hypothetical person that is using a program and providing input for it. Sometimes called the end user
Who is a programmers customer?
Any person, group, or organization that is asking you to write a program
Ovals
Appear at the top and bottom of the flowchart. Terminal symbols. The START terminal symbol marks the program's starting point, and the END terminal symbol marks the program's ending point.
Program Development Cycle
Design the program Write the code Correct syntax errors Test the programs Correct logic errors
Pseudocode
Fake code. Informal language that has no syntax rules and is not meant to be compiled or executed. Instead programmers use pseudocode to create models, or 'mock-ups' of programs
Argument
Inside the parentheses, you type an argument, which is the data that you want displayed on the screen. Like Hello World. Quote marks specify the beginning and the end of the text you wish to display
A ___ error does not prevent the program from running, but causes it to produce incorrect results
Logic
value1 = 99 value2 = 45.99 value3 = 7.0 value4 = 7 value5 = 'abc'
1 = int 2 = float 3 = float 4 = int 5 = str
End-line comments
A comment that appears at the end of a line of code. It usually explains the statement that appears in that line
Flowchart
A diagram that graphically depicts the steps that take place in a program. There are three types of symbols in the flowchart: ovals, parallelograms, and a rectangle
nested function
A function's parameters, plus any variables that are bound (by assignment or by other binding statements, such as def) in the function body, make up the function's local namespace, also known as local scope. Each of these variables is known as a local variable of the function.
Variable
A name that represents a value stored in the computer's memory. Like TAXA CAN REPRESENT THE VALUE IN MEMORY.
Function
A piece of rewritten code that performs an operation. Like print('')
String
A sequence of characters that is used as data is called a string. 'Hello World'
Algorithm
A set of well-defined logical steps that must be taken to perform a task
What is a software requirement?
A single function that the program must perform in order to satisfy the customer.
This operator performs division, but instead of returning the quotient it returns the remainder.
%
an operator that raises a number to a power
**
symbols
+ - * / (floating point number) // (whole number division) % (remainder, divides one number by another and gives the remainder)
string concatenation
+ so the print function can span multiple lines it joins the string together