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Mastering Python Lists

ericchapman profile image Eric Chapman ・2 min read

Hi, here are common Pyton List Manipulation methods.

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In Python, List are a collection of items is particular order. You can put anything you want into a List.

By convention normally you will make the name your List plural. For example a list of person can be name people.

Python use square bracket [] to indicate a List, and individual elements are separated by commas.

List is zero base. That mean the first position is 0 and the second position is 1, etc.

# Create a list
fruits = ['orange', 'apple', 'melon']

# Accessing a List element
fruits[0]  # first item
fruits[-1] # last item

# Append to List
fruits.append('banana')

# Insert to List at position x
fruits.insert(1, 'banana') # will be insert second in the List

# List length
nb_items = len(fruits) # 4

# Remove from list
del fruits[1]   # remove apple

# Remove and return last element
lastFruit =  fruits.pop()   # remove last and return it's value into lastFruit

# Slice my_list[start:finish:step] ([::-1] reverse list) 
fruits = fruits[1:3]
fruits[:3]  # first 3
fruits[2:]  # last 2
copy_fruits = fruits[:] # copy 

#Create list from string
colors = 'red, green, blue'.split(', ')

#Reverse a List
colors.reverse()

# Array concact
color1 = ['red', 'blue']
color2 = ['green', 'yellow']
color3 = color1 + color2

# Concat by unpacking
color3 = [*color1, *color2]

# Multiple assignment
name, price = ['iPhone', 599]

#Create a Tuple (kind of read only list)
colors = ('red', 'green', 'blue')

# Sort
colors.sort() # ['blue', 'green', 'red']
colors.sort(reverse=True) # ['red', 'green', 'blue']
colors.sort(key=lambda color: len(color)) # ['red', 'blue', 'green']

# Looping in a List
for color in colors:
  print(color)

# Generate a List of numbers
numbers = List(range(1, 10)) # 1 2 3 4 5 6 7 8 9

# List comprehension offers a shorter syntax when you want 
# to create a new list based on the values of an existing list.

# Example of long version
fruits = ["apple", "banana", "cherry", "kiwi", "mango"]
newFruits = []

for x in fruits:
  if "a" in x:
    newFruits.append(x)

print(newFruits)

# Same example with List Comprehension 
fruits = ["apple", "banana", "cherry", "kiwi", "mango"]

newFruits = [x for x in fruits if "a" in x]
# Syntax:   [expression for item in iterable if condition == True]

print(newFruits)
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