week 3 - types Flashcards
string
sequence of characters that can be stored in a variable, immutable
string literal
string value specified in the source code of the program
sequence type
type that is a specified collection of objects ordered from left to right
position in sequence is called index
len()
function that returns number of elements in a sequence type
brackets []
used to index a sequence type
alphabet[0] returns…
A
alphabet[-1]
last character (Z)
how to update strings
assign an entirely new string, you can’t edit because its immutable
string concatenation
adding a new character at the end of a string
container
construct to group related values together and contain references to other objects instead of data
list
container created by sequence of variables or literals with brackets
element
list item
index
position of element in list, starting with 0
updating list elements
lists are mutable and can change through re-assignment
method
instructs object to preform some action, executed by specifying method name with “.” and object identifier
append.identifier(value)
adds value to end of list
pop.identifier(1)
removes element at index
remove.identifier(value)
removes first element that matches value
sequence type function
built in functions that operate on sequences like lists/strings
sequence type methods
methods built into class definitions of sequences like lists/strings
list.index(v)
find index of 1st element who’s value is v
list.count(v)
count occurrences of v in list
tuple
immutable collection of data, sequence type
made with paranthesis
when are tuples usually used?
when element position is important
named tuple
allows program to define a simple new data type that consists of named attributes
car.price
car.horsepower
what’s the name of the tuple?
car
what must you do to use named tuples?
import namedtuple
creating named tuples
car = namedtuple(‘car’, [‘make,’, ‘mode’, ‘price’])
set
unordered collection of unique elements, sequential obj only
does a set have postions/indeces?
NO
can more than one element share the same value in a set?
NO
set()
function to make a set, elements can be lists, tuples, strings, etc. used to make empty sets
set literal
written using {}
set.add()
places new elements into the set
set.remove()
takes out specific element from set
set.pop()
takes out random element from set
set1.update(set2)
adds elements of set2 to set1
set1.clear()
removes all elements from set
set.intersection(set1, set2, set3)
returns new set only with elements in common between set and inserted sets
set.union(set1, set2, set3)
returns new set with all unique elements between sets
set.difference(set1, set2, set3)
only returns set elements not found in inserted sets
set.symmetric_difference(setb)
returns elements only with elements once in either a or b
max(list)
finds max value in list
sum(list)
adds all numeric elements in list
set.sort()
rearranges biggest to smallest
string.split()
splits string into list, default delimiter is space
dictionary
collection of key value pairs where you can quickly look up values if you know the key
accessing certain key in dictionary
age[‘ellen’]
list(), tuple()
conversion functions
dict
object type for dictionary
key
term located in dictionary that is associated with a value, immutable
value
describes some data associated with key, ex: definition
making a dictionary
players = {‘Messi’: 10, ‘Ronaldo’: 7}
empty dictionary
{}
accessing dictionary entries
index with specific key in brackets
keyerror
runtime error
adding new entry to end of dict
prices[‘banana’] = 4.00
removing entries
del prices[‘papayas’]
adding entries
dict[k] = v -> adds new key value pair
numeric types
int and float, store data and support normal math operations
mapping types
dict, container where each element is independent with no ordering or relation to other elements
type conversion
convert between types
implicit conversion
automatically made by interpreter, usually through operations
int()
converts float to int without rounding, simply removes fractional part
