week 2 variables Flashcards by Hiba Awais

variable

named storage spot (‘box’) that holds value assigned by three properties

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three properties of a variable

name/identity, type, and value

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int

single whole number, integer

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real values/ floating

decimal (needs bigger ‘box’)

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string

letter(s) “ “

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boolean

true or false

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type function
type()

determines type of variable, can be verified with print

i.e print(type(variable))

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how many numbers can a variable store?

one, it can be altered through reassignment

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defining strings

first = “Ada”
last = “Lovelace”

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concatenating strings

full = first + last
full = “AdaLovelace”
-> no space

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how do you add numbers to a string

convert num to string with str() function

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len(char)

number of characters

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user.lower()

lowercases all alphabets

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indexing username[0]

returns first character, starts at 0

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immutable

cant be changed, strings can’t be altered through indexing

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username[7] = “i”

ERROR.

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string slicing

lets you select sections of a string

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my_str[0:9]

returns first 10 characters

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my_str[10:-5]

does 5 indices after 10, including 10

so basically 10 11 12 13 14 15

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my_str[8:]

everything after 8

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my_str[:8]

everything before 8

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my_str[:-1]

everything but last character

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find(x)

returns the index of the first occurrence of string x

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power sign

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integer division, number without remainder

modulus, remainder

26 // 5

26 % 5

module

library in python that has list of functions

format()

used to format output specified in string before

print("Total Cost: ${:.2f}".format(cost))

formats the cost by adding a dollar sign and only including two numbers after the decimal point

incrementing

increasing a variable's value by 1

identifiers

names used by a programmer for items, sequences of letters, numbers and underscore

a identifier must start with...

letter or underscore, and its case-sensitive

PEP 8

python enhancement proposal, which outlines the basics of python. it suggests identifiers should be lowercase with underscore between words

object

represents a value and is automatically created by the interpreter when executing a line of code

examples of objects

integers, strings, functions, lists, etc

temporary versus permanent objects

print(2+2) is temp x = 7 is permenant

garbage collection

deleting unused objects to free memory space

name binding

associating names with interpreter object

properties of objects

value, type, and identity

immutable types

integers and strings, they can only be reassigned in new objects

id()

gives value of object identity

print(id('ABC'))

create and print identity of a string

floating point literal

written with fractional part even if its a whole number (like 0.0, 1.0, 9.0, etc)

scientific notation

representing super large or small numbers in terms of e

max floating point number

1.8e308

min floating point number

2.3e-208

overflow

when value is too large to be stored in memory allocated by interpreter

float should be used for...

measured values (ex: temperature)

int should be used for...

counted values (ex: students)

when specifying format, python ___ last digit

rounds

expression

combo of items like vars, literals, operators, and parenthesis, that evaluate to a value ex: 2* (x + 1)

literal

specific value in code (ex: 2)

operator

symbol that preforms built-in calculation

precedence rules

ordered standard mathematics. PEMDAS () first ** second - negative third * / % mult, div, and % fourth + - add, sub, fifth evaluate left to right for equal precedence

compound operators

shorthand to update variables

age += 1

age = age + 1

age -= 1

age = age - 1

age *= 1

age = age * 1

age /= 1

age = age / 1

age %= 1

age = age % 1

floor division, rounds down and returns integer

5.0 // 2

2.0 if operand is float, returns float

script

python program written in a file which is passed to python interpreter as input

import

statement that makes module available for use ex: import math

dot notation

used to access objects defined in module

if module is universe and variable is speed...

universe.speed

when imported, ____ code in module executes

all

math module

standard python module that supports advances mathematics operations

function

list of statements that can be executed by referencing functions name

function call

process of invoking function

argument

item passed to a function

unicode

code that represents every possible character as a unique number ASCII

code point

unique numbers in unicode

escape char \\

single backslash

escape char \'

single quote

escape char \"

double quote

tab/indent

raw string

ignores the escape sequences, created by adding r before string literal

ord()

returns encoded integer value for string of length 1 ex: ord('H') returns 72

chr()

returns string of one char for encoded int ex: chr(72) returns 'H'