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Vicki Langer
Vicki Langer

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Charming the Python: Lists

#python #beginners

If coding tutorials with math examples are the bane of your existence, keep reading. This series uses relatable examples like dogs and cats.

Lists

A list is a collection which is ordered and changeable and there may be duplicate items.

Creating a List 

# creating a list with a builtin function list_name = list('list item 1', 'list item 2', 'list item 3') # creating a list with brackets another_list_name = ['list item 1', 'list item 2', 'list item 3'] # you can create an empty list like this list = []
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Accessing list items using indexing

cat dog mouse cheese lemon road
0 1 2 3 4 5
-6 -5 -4 -3 -2 -1 
things = ['cat', 'dog', 'mouse', 'cheese', 'lemon', 'road'] print(things[0]) >>>cat print(things[-2]) >>>lemon
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Changing Lists

Lists are mutable, or modifiable.

Add via Index 

things = ['cat', 'dog', 'mouse', 'cheese', 'lemon', 'road'] # our list things[0] = 'chair' # adds 'chair' to the beginning of list, at index 0 print(things) # returns newly modified list >>>['chair', 'cat', 'dog', 'mouse', 'cheese', 'lemon', 'road']
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Add to end 

things = ['cat', 'dog', 'mouse', 'cheese', 'lemon', 'road'] # our list things.append = 'chair' # adds 'chair' to the end of list print(things) # returns newly modified list >>>['cat', 'dog', 'mouse', 'cheese', 'lemon', 'road', 'chair']
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Check 

things = ['cat', 'dog', 'mouse', 'cheese', 'lemon', 'road'] # our list does_exist = 'banana' in things # sees if 'banana' is in the list print(does_exist) >>>True does_exist = 'lime' in things # sees if 'lime' is in the list print(does_exist) >>>False
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Insert 

things = ['cat', 'dog', 'mouse', 'cheese', 'lemon', 'road'] # our list things.insert('pie', 1) # adds 'pie' at index 1 print(things) >>>'cat', 'pie', 'dog', 'mouse', 'cheese', 'lemon', 'road'
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Remove 

things = ['cat', 'dog', 'mouse', 'cheese', 'lemon', 'road'] # our list things.remove('mouse') # removes 'mouse', regardless of index print(things) >>>'cat', 'dog', 'cheese', 'lemon', 'road'
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Pop 

things = ['cat', 'dog', 'mouse', 'cheese', 'lemon', 'road'] # our list things.pop(-2) # removes item referenced by index print(things) >>>'cat', 'dog', 'mouse', 'cheese', 'road'
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Delete 

things = ['cat', 'dog', 'mouse', 'cheese', 'lemon', 'road'] # our list del things[0] # deletes item referenced by index print(things) >>>'dog', 'mouse', 'cheese', 'lemon', 'road'
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Clear 

things = ['cat', 'dog', 'mouse', 'cheese', 'lemon', 'road'] # our list things.clear() print(things) # nothing will show because you've cleared all items from the list >>>
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Joining 

things = ['cat', 'dog', 'mouse', 'cheese', 'lemon', 'road'] more_things = ["table", "book", "blanket"] new_list = things + more_things # combines both lists in the order written print(new_list) >>>'cat', 'dog', 'mouse', 'cheese', 'lemon', 'road', "table", "book", "blanket" newer_list = more_things + things print(newer_list) >>>"table", "book", "blanket", 'cat', 'dog', 'mouse', 'cheese', 'lemon', 'road'
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Counting 

things = ['cat', 'dog', 'mouse', 'cheese', 'lemon', 'road'] print(things.count()) >>>6
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Reversing 

things = ['cat', 'dog', 'mouse', 'cheese', 'lemon', 'road'] things.reverse() # flip the order of the list print(things) >>>'road', 'lemon', 'cheese', 'mouse', 'dog', 'cat'
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Sorting 

things = ['cat', 'dog', 'mouse', 'cheese', 'lemon', 'road'] things.sort() # alphanumeric order print(things) >>>'cat', 'cheese', 'dog', 'lemon', 'mouse', 'road' things.sort(reverse=True) # backwards print(things) >>>'road', 'mouse', 'lemon', 'dog', 'cheese', 'cat'
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Series based on

asabeneh

30 Days Of Python Challenge

Asabeneh ・ Nov 20 '19

#python #javascript #react #mongodb

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