Python Test 3 Chapter 10
dictionary; entries
In practice, a programmer first creates a __________ and then adds _______, perhaps by reading user-input or text from a file.
my_dict[key] jose_grade = my_dict['Jose']
Indexing operation - retrieves the value associated with key.
list( ); list
Instead of indexing, a valid approach is to use the list( ) built-in function to convert view object into a ____, and then perform the necessary operations.
wraps braces { } around key-value pairs of literals and/or variables
What is the first (braces) approach to create a dict.
KeyError
What type of error does set.remove(value) raise if a value is not found in the set?
runtime error
What type of error will using the index operator on a set cause?
"named" attribute
Which is simpler to read: a "named" attribute or a list of tuple referenced via index.
A Car named tuple with fields like Car.price and Car.horsepower
Which would more clearly represent a car object: A Car named tuple with fields like Car.price and Car.horsepower or a list with index positions correlating to some attributes.
dictionary comprehension (out of scope for this material)
evaluates a loop to create a new dictionary, similar to how list comprehension creates a new list.
dict[k]=v
updates the existing entry dict[k], if dict[k] already exists
NO
Do sets allow duplicates?
dict(Bobby= '805-555-2232', Johnny='951-555-0055')
Example of dict( ) with key-value pairs
named tuple
allows the programmer to define a new simple data type that consists of named attributes.
no
Can dictionaries be accessed by indexing?
yes
Can you iterate of a dictionary?
set.clear( )
Clears all elements from the set
dot notation
In a named tuple, a data object's attributes can be accessed using what?
hash value
What is ordering determined by in a dictionary?
no
Once created, can a tuple's elements be changed?
yes
Can a diction contain a list?
dict
A dictionary is represented by the ____ object type
set.add(value)
Add value into the set
my_dict[key] = value my_dict['Jose'] = B+
Adds an entry if the entry does not exist, else modifies the existing entry.
set1.update(set2)
Adds the elements in set2 to set1
dict[k]=v
Adds the new key-values pair k-v, if dict[k[ does not already exist
set( )
An empty set can only be created using what?
yes
Are dictionaries mutable?
yes
Are sets mutable?
index operator
Because the elements of a set are unordered and have no meaningful position in the collection, the _____ ________ is not valid.
del dict[k]
Deletes the entry dict[k]
del my_dict[key] del my_dict['Jose']
Deletes the key entry from a dict.
associative
Dictionaries are typically used in place of lists when what type of relationship exists
yes
Do dictionary elements maintain their insertion order.
yes
Do sets support the len( ) function?
no
Do view objects support iterating?
yes
Does a view object reflect any updates made to a dictionary, even if the dictionary is altered after the view object is created?
yes
Does printing a tuple always display surrounding parentheses?
yes
Does the following state produce an error: my_dict.keys()[0]
key; value
Each ________ in the dictionary is associated with a ______, much like each word in an English language dictionary is associated with a definition.
in-place
Ex. the following evaluation of the statement my_dict.pop('Ahmad'), any other variables that reference the same objects as my_dict will also reflect the removal of 'Ahmad'
dict([('Bobby', '805-55-2232'), ('Johnny', '951-555-0055')])
Example of dict( ) with tuple pairs
len(set)
Find the length (number of elements) of the set
the key is specified in brackets [ ].
How does you access a dictionary entry?
by created a list of comma-separated values, such as 5, 15, 20
How is a new tuple generated?
where the name and attribute names of the named tuple are provided as arguments to the namedtuple constructor. (Note that the fields to include in the named tuple are found in a list, but may also be a single string with space or comma separated values)
How should a named tuple be created once the container is imported?
replace the named tuple with a new object
How would a programmer wishing to edit a named tuple go about it?
KeyError
If no entry with a matching key exists in the dictionary, what type of runtime error occurs when the program is terminated?
yes
Is a tuple a sequence type?
immutable
Like normal tuples, named tuples are ___________.
my_dict1.update(my_dict2)
Merges dictionary my_dict1 with another dictionary my_dict2. Existing entries in my_dict1 are overwritten if the same keys exist in my_dict2.
in-place
Modification of dictionary elements using the dictionary methods is performed ___________.
my_dict.get(key, default)
Reads the value of the key entry from the dictionary. If the key does not exist in the dictionary, then returns default.
set.pop( )
Remove a random element from the set
my_dict.clear()
Removes all items from the dictionary.
my_dict.pop(key, default)
Removes and returns the key value from the dictionary. If key does not exist, then default is returned.
dict.items()
Returns a list of dict's (key, value) tuple pairs
set.union(set_a, set_b, set_c...)
Returns a new set containing all of the unique elements in all sets.
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.
1. elements are unordered 2. elements are unique
Sets have the following 2 properties:
set( )
Simply passing a list into _________ will cause any duplicates to be omitted in the created set.
key in my_dict if 'Jose' in my_dict: # . . . .
Tests for existence of key in my_dict.
dict
The ____ type implements a dictionary in Python.
namedtuple
The ________ container must be imported to create a new named tuple.
remove( ); pop( )
These two methods remove an element from the set.
value in set
To check if a specific value exists in a set, a membership test such as _____________ ______ _________ can be used.
parentheses ex. (5, 15, 20)
Typically, tuples are surrounded with _________________.
no elements in the set share the same value
What does it mean that elements are unique?
elements in the set do not have a position or index
What does it mean that elements in a set are unordered?
attempting to create a new entry with a key that already exists in the dictionary replaces the existing entry
What happens when you attempt to create a new entry of a dictionary key that already exists?
chevy_blazer.price
What is an example of dot notation in a named tuple?
tuples
________ are typically used when element position, and not just the relative ordering of elements, is important.
dictionary
a Python container used to describe associative relationships
curly braces{ }
a dict object is created using ________ to surround the key:value pairs that comprise the dictionary contentws
dictionary method
a function provided by the dictionary type (dict) that operates on a specific dictionary object
set()
a set can be created using what function?
key
a term that can be located in a dictionary, such as the word "cat" in the English dictionary.
hash
a transformation of the key into a unique value that allows the interpreter to perform very fast lookup
set()
accepts a sequence-type iterable object (list, tuple, string, etc.) whose elements are inserted into the set.
{'Jose': 'A+', 'Gino': 'C-'}
an example of a dictionary with two keys 'Jose' and 'Gino' that are associated with the grades 'A+' and 'C-', respectively
set
an unordered collection of unique elements.
dictionary
associates (or "maps") keys with values
Tuple
behaves similar to a list but is immutable
dict( )
built-in function, using either keyword arguments to specify the key-value pairs or by specifying a list of tuple-pairs
key
can be any immutable type, such as a number, string, or tuple.
set literal
can be written using curly braces { } with commas separating set elements.
value
can by any type
dictionaries
can contain objects of arbitrary type, even other containers such as lists or nested dictionaries
Dictionaries
contain references to objects as key-value pairs
values
describes some data associated with a key, such as a definition.
len( )
function that returns the number of elements in a set.
set
often used to reduce a list of items that potentially contains duplicates into a collection of unique values.
namedtuple()
only creates the new simple data type and does not create new data objects.
view object
provides read-only access to dictionary keys and values
set.remove(value)
remove the element with given value from the set. Raises KeyError if the value is not found.
dict.keys()
returns a view object that yields dictionary keys
dict.values()
returns a view object that yields dictionary values
sequence type
supports len(), indexing, and other sequence type functions
del
this keyword is used to remove entries from a dictionary
dict.items( )
this method is particularly useful, ass the view object that is returned produces tuples containing the key-value pairs of the dictionary.
add( )
this method places a new element into the set if the set does not contain an element with the provided value.
