Chapter 3 CS453 Python

What do Dictionaries do

They map keys to values; no ordering is maintained between entries

What does list.index(val) do?

This function finds the index of the first element within the list whose value matches the val

What is a String

a String is a series of characters,like the text Mary, that can be stored in a variable

What is a word for a term that can be located on a dictionary

a key

What is a method?

a method instructs an object to perform some action and is executed by specifying the method name following a "."

what is the result of a set([100, 200, 100, 200, 300])

a set containing elements 100, 200, 300,

Since sets are unordered, this means you can't

access the element within the set by using index because it does not have an index

Since sets are mutable elements can be

added or removed using set methods

what does set1.update(set2)

adds the elements in set2 to set 1

How do you access list elemetns

by using indexing expression

attribute error

can be defined as an error that is raised when an attribute reference or assignment fails.

set.clear( )

clears all elements from the set

Element index

contained elements are ordered by position in the list

A value

describes some data associated with a key

How do you add new entries to a dictionary

dict[k]= v: Adds the new key-value pair k-v, if dict[k] already exist

Simply passing a list into a set ( ) will cause any

duplicates to be omitted in the created set.

the \ characters after the string literal _______-

extends the string to the following line

Container

is a construct used to group related values together and contains references to other objects instead of data

List

is a container created by surround a sequence of variables of literals with brackets []

element

is a list item

Dictionary

is a python container used to describe associative relationships it is represented by the dict object type

What is String literal

is a string value specified in the source code of the program example: 'MARY' OR "MARY" usually have single or double quotes

Sequence type

is a type that specifies a collection of objects ordered form left to right.

String concatenation

is the process of adding new characters to a string

len() function

is used to find the length of a string

What function is used to find the length of a list

len(list)

What does the append method look like?

list.append(value): Example list.append('abc')

What does the pop method look like in python

list.pop(i): Removes the element at index i from list.

What does the remove method look like?

list.remove(v): Removes the first element value is v

what function causes the concatenation of one or more list t

list1 + list2

How do you find the element with the largest value on a list

max(list)

Create a set using the set function

num_christians= set( 30, 32, 53)

What does namedtuple( ) do?

only creates new simple data type, and does not create new data objects Above, a new object is not created until car( ) is called appropriate values.

The add ( ) method

places a new element within a set if the set does not contain an element with the provided value

you can use the remove and pop methods to

remove an element in a set

Set.pop(

removes a random element from the set

set.remove(value)

removes value from the set. Raises KeyError if value is not found.

What is an example of adding elements to a set

set.add(value): Add value into the set Ex: my_set.add( 'abc')

What are some examples of removing elements form a set:

set.remove(value): Remove the element with the given value from the set. Raises Key Error if the value is not found. set.pop(value) removes a random element in the set

How do you find the sum of all the elements of a list?

sum(list)

How can a named tuple be created

the named tuple package must be imported to create a new named tuple.

Elements can be removed using

the pop() or remove methods

Set is often used to___

to reduce a list of items that potentially contains duplicates into a collection of unique values

How do you remove entries from the dictionary

using the Del keyword del prices [ 'papaya'] removes the entry whose key is 'papaya'

Are dictionaries mutable?

yes,

What is an example of a named tuple

A Car named tuple with fields like Car.price and Car.horsepower would more clearly represent a car object than a list.

what does len(set) do

Finds the length of the set

set.union(set_a, set_b, set_c...)

Returns a new set containing all of the unique elements in all sets.

String type is a special construct known as a _____________

Sequence type

what are sequence type functions

They are built in functions that act on list and strings

How to add elements to list

Use the append list method is used to add new elements to a list

set.add(value)

adds value into the set

What does len(set1)

looks at the length of set1

Create a set using a set literal

num_Christians = {30, 32, 55}

Important note: an empty set can only be created by using

set ( )

What are the two ways to create a set

using the set ( ) function or by using a set literal

What is the main difference between a tuple and a list

A tuple is immutable whereas a list is mutable

How do you build a dictionary

Curly Braces { }

What is an unordered collection of unique elements

Set

What is this an example of "New" + "York"

String concatenation

What are sequence-type methods

They are methods built into the class definition of sequences like strings and list

What are so special about list

They are mutable, this means that a programmer can use methods to add and remove elements for ma list as needed

How do you find the the element with the smallest value in a list

min(list)

You can use negative indexes

-1 means last character in a string

How can you make a named tuple of a NBA and NFL player

1. Import named tuple 2. Player = namedtuple( 'Player', [ 'name', 'number', 'position', 'team'] 3 cam= Player( 'Cam Newton', '1', 'Quarterback', 'Carolina Panthers 4. lebron= Player( 'Lebron James', '23', 'Small Forward', 'Los Angeles lakers') 5. print (cam.name + '( ' # + cam.number + ')' + ' is a ' + cam.position + ' for the ' + cam.team + '.') 6. print (lebron.name + ' ( ' # + lebron.number + ' ) ' + 'is a ' + lebron.position + ' for the' + lebron.team + ' . ')

What are some qualities of a set

1. The elements are unordered: So the elements do not have a position or an index. 2. Elements are unique: No elements in the set share the same value

How do you access key entry

A key is placed in brakcets [ ] to acces a speicific dictionary entry.

How is a dictionary entry added

A new dictionary entry is added by using backets to specify the key: prices ['banana'] =1.49.

How do you create a tuple?

A tuple is created by creating a list with comma-separated values such as 5, 15, 20

what is associative relationships

Associative relationships exist between records that are conceptually close, but where the relationship is neither equivalent nor hierarchical. The most basic type of associative relationship is simply related to.

Why are list so important

Because it is essential for reducing the number of variables in a program by storing an entire collection of related variables

Why must you use an assignment statement when updating a string

Because strings are immutable objects

How come String concatenation doesn't contradict the immutability of strings

Because the result of a string concatenation is a new string; the original string is not altered.

How can you access the elements in a list?

By accessing the index function in the list Example: List[0] will show the value stored in element 0 of List1

How do you create a new named tuple

By importing the named-tuple package Example: Import namedtuple

How do you create a set

By using the function set( )

what does list.count(val)

Count the number of occurrences of the value val in list

Players = { 'Lionel Messi': 10, 'Cristiano Ronaldo': 7 }

Creates a dictionary called players with two keys: 'Lionel Messi' and 'Cristiano Ronaldo' and values 10 and 7

What is so important about a named tuple

It allows the programmer to define a new simple data type that consists of named attributes.

what is so important about the input function in python

It can be used to get the strings from the user

When would using a tuple be important

It can be used when element position, and not just relative ordering of elements is important

A set is similar to a list because

It does not matter what order the elements are in

How is a dict object created

It is created by using curly braces { } to surround the key:value pairs that comprises the dictionary contents

How do you create an empty dictionary

It is created with the expression player = { }

Set. intersection (set_a, set_b, set_c)

Returns a new set containing only the elements in common between set and all provided sets.

set_a.symmetric_difference(set_b)

Returns a set containing only elements that appear in exactly one of set_a or set_b

set.difference(set_a, set_b, set_c...)

Returns a set containing only the elements of set that are not found in any of the provided sets.

What does the set function accept

The set function accepts a sequence-type iterable object (list, tuple, string, etc )`