Ch 2 Variables and Assignments ver 2
5/10
0.5
x = 5 x = x + 7
12
num_atoms is initially 7. What is num_atoms after: num_atoms *= 2?
14
x = 2 y = 3 x = x * y x = x * y
18
5.0//2
2.0
12/4
3.0
596%10
6
identifier (variable name)
Also called a name, is a sequence of letters (a-z,A-Z), underscores(_), and digits(0-9). Identifiers must start with a letter or an underscore.
Reserved Words
Also called keywords, are words that are part of the language and cannot be used as a programmer-defined name. Many programs automatically color a program's reserved words
escape sequence
An escape character, \, followed by one or more printable characters used to designate a nonprintable character.
Evaluates
An expression evaluates to a value, which replaces the expression
type()
Built-in function that prints the type of an object
What is total_count after executing the following? num_items = 5 total_count = 1 + (2 * num_items) * 4
41
78%10`
8
x = 9 y = x + 1 What is x?
9
float
A data type in programming that contains a floating point value, more commonly referred to as a decimal value, like 1.5 or 3.14
Module
A file containing Python code that can be used by other modules or scripts
Script
A file where programmers typically write Python program code, and executes the code by passing the script as input to the Python interpreter.
scientific notation
A floating-point literal using scientific notation is written using an e preceding the power-of-10 exponent, as in 6.02e23 to represent 6.02x1023. The e stands for exponent. Likewise, 0.001 is 1x10-3, so it can be written as 1.0e-3.
\\
Backslash (\) print('\\home\\users\\') \home\users\
\"
Double-quote (") print("He said, \"Hello friend!\".") He said, "Hello friend!".
y = 30 x = y + 2 x = x + 1
33
math module
Supports advanced math operations
Case Sensitive
Uppercase and lowercase letters are different. Cat and cat hat and Hat
Variable
a named item used to hold a value x num_people
literal
a specific value in code, like 2
Operator
a symbol that performs a built-in calculation, like +, -,*,/,**
2x
not valid
OverflowError
occurs when a value is too large to be stored in the memory allocated by the interpreter
backslash
upon reaching a \, the interpreter recognizes that item as the start of a special character's two-item sequence and then looks at the next item to determine the special character.
Floored division operator //
used to round down the result of a floating-point division to the closest whole number value 20//10=2 50//50=1 5//10=0 (remainder 5 is thrown away)
2
valid
2 * (x - y)
valid
x
valid
x + 1
valid
x=1
valid
x=y
valid
x=y+2
valid
y + 2 * z
y+(2*z)
Complete this statement to increment y: y = _____
y+1
6 + num_items
yes
num_atoms is initially 7. What is num_atoms after: num_atoms += 5?
12
51%2
1
x = 9 y = x + 1 What is y?
10
x = 9 y = x + 1 x = 5 What is y?
10
What is the output of print('10...\n9...')
10... 9...
function
a list of statements that can be executed by simply referring to the function's name
Exponent
**, as in x**y
Multiplication
*, as in x*y
Addition
+, as in x+y
Subtraction
-, as in x-y
assignment statement
-assigns a variable with a value x=5 means x is assigned with 5 and keeps that value during subsequent statements, until x is assigned again. -left side must be a variable -right side can be an expression -A statement can be x=5, y=x, z=x+2
Division
/,as in x/y
50%2
0
100%(1//2)
error
100/0
error
Modulo Operator
evaluates to the remainder of the division of the two integer operands 23%10 is 3
Import
executes the contents of a file containing Python code and makes the definitions from that file available
A person's height in centimeters
float
The average number of kids per household
float
The current temperature in Celsius
float
incrementing
increasing a variable's value by 1, as in x=x+1
The number of cars in a parking lot
int
The number of hairs on a person's head
int
3rd_place
invalid
num cars
invalid
x+1=3
invalid
x+y=y+x
invalid
5t
no
6 x num_items
no
n factorial n!
no. Python does not use ! symbol for factorial
argument
the item passed to a function. some functions have multiple arguments.
function call
the process of invoking a function
module
Python code located in another file
\'
Single-quote (') print('Name: John O\'Donald') Name: John O'Donald
\t
Tab (indent) print('1. Bake cookies\n\t1.1. Preheat oven') 1. Bake cookies 1.1. Preheat oven
Dot notation
Used to reference an object in an imported module
Unicode
Used to represent every possible character as a unique number, known as code point
Is the following an error? num_years = 1,999,999,999
Yes. -Commas are not allowed in an integer literal.
What is the output of print('\\c\\users\\juan')
\c\users\juan
expression
a combination of items, like variables, literals, operators, and parentheses, that evaluates to a value, like 2*(x+1)
floating-point number
a real number, like 98.6, 0.0001, or -666.667. Floating-point refers to the decimal point being able to appear anywhere in the number
Given a 16-digit credit card number stored in x, which gets the last (rightmost) four digits? (Assume the fourth digit from the right is non-zero).
x%10000
The negative of user_val: -user_val
yes
total_days / 12
yes
What is the output of print('My name is \'Tator Tot\'.')
My name is 'Tator Tot'.
\n
Newline print('My name...\nIs John...') My name... Is John...
2+(xy)
not valid
y=x+1
not valid
Division operator /
performs division and returns as a floating-point number. 20/10=2.0 50/50=1.0 5/10=0.5
floating-point literal
written with the fractional part even if that fraction is 0, as in 1.0, 0.0, or 99.0
__numcars2
valid
_num_cars
valid
numCars
valid
num_cars1
valid
third_place
valid
