1.2 Python Data Structures, String, Date and Time Flashcards
A data structure in Python that is ordered and mutable (changeable)
List [ ]
Items in this data structure do not need to be homogenous or of the same type
List
Elements in this data structure are indexed according to a definite sequence and the indexing is done with 0 being the first index
List
A list inside a list is called
Nested list
It can have any number of items and they may be of different types (integer, float, string etc)
List
The index of -1 refers to the last item, -2 to the second last item and so on
Negative indexing
Add an element to the end of the list
append()
Add all elements of a list to the end of another list
extend()
Insert an item at the defined index
insert()
Removes an item from the list
remove()
Removes and returns an element at the given index
pop()
Removes all items from the list
clear()
Returns the index of the first matched item
index()
Returns the count of number of items passed as an argument
count()
Sort items in a list in ascending order
sort()
Reverse the order of items in the list
reverse()
Returns a shallow copy of the list
copy()
This data structure is an unordered collection of items. Every element is unique (no duplicates) and immutable (cannot be changed)
Set { }
Although a set element is immutable, a set itself is _____________. We can add or remove items from it
mutable
A set cannot have mutable elements like lists, sets, or ______________ as its elements
dictionaries
Adds an item to a set
add()
Adds multiple items to a set
update()
To remove an item in a set, use the remove() or _________ method
discard()
If the item to remove does not exist in a set, __________ will raise an error
remove()
If the item to remove does not exist, __________ will NOT raise an error
discard()
Using ________ will remove the last item
pop()
This method empties the set
clear()
This keyword deletes the set completely
del
Returns a new set with all items from both sets; symbolized by | operator
Union
Returns a new set with Common Elements from both sets; symbolized by & operator
Intersection
To find difference in between sets; symbolized by - operator
Difference
To find difference from both sets; symbolized by ^ operator
Symmetric Difference
A data structure in Python that is ordered and immutable (unchangeable)
Tuple ( )
A tuple can be created without parentheses. This is called
tuple packing
Ways to Access a Tuple
- Postive Indexing
- Negative Indexing
- Slicing
Returns the number of items (x) in a tuple
count(x)
Returns the index of the first item that is equal to x
index(x)
An unordered collection of items that is mutable
Dictionary
____ of a dictionary must be unique and immutable data type such as strings, integers, and tuples
Keys
This dictionary method returns None instead of KeyError, if the key is not found
get()
This method removes an item with the provided key and returns the value
pop()
This method can be used to remove and return an arbitrary (key, value) item pair from the dictionary
popitem()
Returns a new dictionary with keys from seq and value equal to v (defaults to None)
fromkeys(seq[,v])
Returns the value of the key. If the key doesn’t exist, returns d (defaults to None)
get(key[,d])
Return a new object of the dictionary’s items in (key, value) format
item()
Returns a new object of the dictionary’s keys
keys()
Removes the item with the key and returns its value or d if key is not found. If d is not provided and the key is not found, it raises KeyError
pop(key[,d])
Returns the corresponding value if the key is in the dictionary. If not, inserts the key with a value of d and returns d (defaults to None)
setdefault[key[,d])
Updates the dictionary with the key/value pairs from other, overwriting existing keys
update([other])
Returns a new object of the dictionary’s values
values()
Returns True if all keys of the dictionary are True (or if the dictionary is empty)
all()
Return True if any key of the dictionary is true. If the dictionary is empty, return False
any()
Return the length of dictionary
len()
Compares items of two dictionaries (Not available in Python 3)
cmp()
Return a new sorted list of keys in the dictionary
sorted()
Create a datetime object containing the current local date and time using this method
now()
Use this method defined in the date class to get a date object containing the current local date
today()
Commonly used classes in datetime module are:
- date Class
- time Class
- datetime Class
- timedelta Class
You can convert a timestamp to date using this method
fromtimestamp()
A class from datetime module that contains information from both date and time objects
datetime.datetime Class
Print year, month, hour, minute and timestamp
datetime.datetime Class
Represents the difference between two dates or times
datetime.timedelta
This method is defines under classes date, datetime and time. Creates a formatted string from a given date, datetime or time object. Ex.: %Y, %m, %d etc
strftime()
