Implement Array Lists In Python
An array specifies a variable that can be indexed as a list in rows and columns.
The first index is zero as is common is most programming languages. Python does not have an array data type. Instead the data type list, tuple, set or dictionary can be used.
A list is a collection which is ordered and changeable allowing duplicate members. Lists are created using square brackets..
Common Functions For Manipulating Lists In Python
Common List Functions
| Name | Description | Example |
|---|---|---|
| len() | Determine how many items | len(even_numbers) |
| append() | Append items | even_numbers.append(12) |
| insert() | Insert item at specified index | even_numbers.insert(1, 2) |
| remove() | Remove specified item | even_numbers.remove(2) |
| pop() | Pop the item at specified index | even_numbers.pop(1) |
| del | Delete the item at specified index | del even_numbers[1] |
| clear() | Remove all values | even_numbers.clear() |
| sort() | Sort in ascending order | even_numbers.sort() |
| reverse() | Sort in reverse order | even_numbers.reverse() |
| copy() | Make a copy | even_numbers.sort() |
| extend() | Add elements from one list | list1.extend(list2) |
| count() | Returns number of elements with specified value | list1.count(2) |
| index() | Returns index of first element with specified value | list1.count(4) |
| Name | Description | Example |
Python List Snippet
# OjamboShop.com Learning Python Array List Tutorial #
even_numbers = [2,4,6,8,10]
print(even_numbers)
print(len(even_numbers)) # Number Of Items In List
duplicate_list = [2,4,6,8,10,2,4,6,8,10]
print(duplicate_list)
print(duplicate_list[1]) # Access List Item By Index Number
print(duplicate_list[2:5]) # Range Of Indexes
even_numbers[4] = 12 # Change Item Value By Index Number
print(even_numbers)
even_numbers.append(14) # Add Item To End
print(even_numbers)
even_numbers.insert(1, 2) # Insert Item Value At Index Number
print(even_numbers)
even_numbers.remove(2) # Remove Item Value
print(even_numbers)
even_numbers.pop(1) # Pop Item At Index Number
print(even_numbers)
del even_numbers[1] # Remove Item At Index Number
print(even_numbers)
even_numbers.clear() # Remove All Items
print(even_numbers)
even_numbers.sort() # Sort All Items In Ascending Order
print(even_numbers)
even_numbers.reverse() # Sort All Items In Reverse Order
print(even_numbers)
copied_list = even_numbers.copy() # Make A Copy
print(copied_list)
list1 = ["John", "Jake"]
list2 = even_numbers.copy()
list3 = list1 + list2 # Join Two Lists
list1.extend(list2) # Add Elements From One List
print(list1)
print(list3)
print(list1.count("John")) # Returns Number Of Times The Value "John" Appears
print(list1.index("John")) # Returns Index Of First Time The Value "John" Appears
Usage
You can use any IDE or text editor and the command line to compile and execute Python code. For this tutorial, the OjamboShop.com Learning Python Course Web IDE can used to input and compile Python code for lists.
Open Source
Python is licensed under the Python Software Foundation License. This allows commercial use, modification, distribution, and allows making derivatives proprietary.
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Conclusion:
Python makes it easy to use lists. Use lists when you need an ordered, changeable array that might have duplicate members.
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