background

Two days ago, we studied together. Python Variables, Operators and Data Types And the most commonly used in programming Branch statement and loop statement.

Today, let's learn about one of the most common structures in Python: lists, and another similar structure: tuples.

code implementation

1. List

• Lists are ordered collections with no fixed size and can store any number of Python objects of any type.

Create lists

• Create a common list

week = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday']
print(week)  # ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday']

number = [2, 3, 4, 5, 6, 7]
print(number)  # [2, 3, 4, 5, 6, 7]

• Create a mixed list

mix = [1, 'lsgo', 3.14, [1, 2, 3]]
print(mix)  # [1, 'lsgo', 3.14, [1, 2, 3]]

• Create an empty list

empty = []
print(empty)  # []

Adding elements to the list

• Appnd (obj) method: Add a new object at the end of the list

week = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday']
week.append('Thursday')
print(week)  # ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Thursday']
print(len(week))  # 6

• Extension (seq) method: Append multiple values in another sequence at the end of the list at once (expand the original list with a new list)

week = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday']
week.extend(['Thursday', 'Sunday'])
print(week)  # ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Thursday', 'Sunday']

• insert(index, obj) method:

week = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday']
week.insert(0, 'Sunday')
print(week)  # ['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday']

Get elements from the list

• Like arrays, we can get a single element from the list by the index value of the element. Note that the index value of the list starts at 0.

week = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday']
print(week[0])  # Monday

Delete elements from the list

• remove(obj) method: Remove the first match of a value in the list

week = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday']
week.remove('Monday')
print(week)  # ['Tuesday', 'Wednesday', 'Thursday', 'Friday']

• del var1[, var2... ] Statement: Delete one or more objects

week = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday']
del week[0], week[1]
print(week)  # ['Tuesday', 'Thursday', 'Friday']

• pop([index=-1]) method: Remove an element from the list (default last element) and return the value of that element

week = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday']
day = week.pop()
print(day)  # Friday
day = week.pop(0)
print(day)  # Monday
day = week.pop(-2)
print(day)  # Wednesday

List fragmentation

Example 1:

week = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday']
print(week[1:3])  # ['Tuesday', 'Wednesday']
print(week[:3])  # ['Monday', 'Tuesday', 'Wednesday']
print(week[3:])  # ['Thursday', 'Friday']
print(week[:])  # Copies of week ['Monday','Tuesday','Wednesday','Thursday','Friday']

Example 2:

list1 = [123, 456, 789, 213]
list2 = list1
list3 = list1[:]
print(list2)  # [123, 456, 789, 213]
print(list3)  # [123, 456, 789, 213]
list1.sort()
print(list2)  # [123, 213, 456, 789] 
print(list3)  # [123, 456, 789, 213]

Common operators of lists

• Comparison operator
• Logical Operator
• Connection operator+
• Repeat operator*
• Membership operators in, not in

list1 = [123, 456]
list2 = [234, 123]
print(list1 > list2)  # False

list3 = [123, 456]
print((list1 < list2) and (list1 == list3))  # True

list4 = list1 + list2  # extend()
print(list4)  # [123, 456, 234, 123]

list5 = list3 * 3
print(list5)  # [123, 456, 123, 456, 123, 456]

list3 *= 3
print(list3)  # [123, 456, 123, 456, 123, 456]

print(123 in list3)  # True
print(456 not in list3)  # False

Other methods of listing

• count(obj) method: counting the number of times an element appears in a list

list1 = [123, 456] * 3
print(list1)  # [123, 456, 123, 456, 123, 456]
num = list1.count(123)
print(num)  # 3

• index(obj[, start[, end]]) method: Find the index location of the first match of a value from the list

list1 = [123, 456] * 5
print(list1.index(123))  # 0
print(list1.index(123, 1))  # 2
print(list1.index(123, 3, 7))  # 4

• reverse() method: elements in the reverse list

list1 = [123, 456, 789]
list1.reverse()
print(list1)  # [789, 456, 123]

• sort(key=None, reverse=False) method: Sort the original list

list1 = [123, 456, 789, 213]
list1.sort()
print(list1)  # [123, 213, 456, 789]

list1.sort(reverse=True)
print(list1)  # [789, 456, 213, 123]

2. Tuples

Create and access a tuple

• Python tuples are similar to lists, except that tuples cannot be modified after they are created, similar to strings.
• Tuples are bracketed and lists are bracketed.
• Tuple creation is simple, just add elements in parentheses and use commas to separate them.

tuple1 = (1, 2, 3, 4, 5, 6, 7, 8)
print(tuple1[1])  # 2
print(tuple1[5:])  # (6, 7, 8)
print(tuple1[:5])  # (1, 2, 3, 4, 5)
tuple2 = tuple1[:]
print(tuple2)  # (1, 2, 3, 4, 5, 6, 7, 8)

• When only one element is contained in a tuple, a comma is added after the element, otherwise parentheses are used as operators:

Example 1:

temp = (1)
print(type(temp))  # <class 'int'>
temp = 2, 3, 4, 5
print(type(temp))  # <class 'tuple'>
temp = []
print(type(temp))  # <class 'list'>
temp = ()
print(type(temp))  # <class 'tuple'>
temp = (1,)
print(type(temp))  # <class 'tuple'>

Example 2:

print(8 * (8))  # 64
print(8 * (8,))  # (8, 8, 8, 8, 8, 8, 8, 8)

Update and delete a tuple

Example 1:

week = ('Monday', 'Tuesday', 'Thursday', 'Friday')
week = week[:2] + ('Wednesday',) + week[2:]
print(week)  # ('Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday')

Example 2:

t1 = (1, 2, 3, [4, 5, 6])
print(t1)  # (1, 2, 3, [4, 5, 6])

t1[3][0] = 9
print(t1)  # (1, 2, 3, [9, 5, 6])

Tuple-related operators

• Comparison operator
• Logical Operator
• Connection operator+
• Repeat operator*
• Membership operators in, not in

t1 = (2, 3, 4, 5)
t2 = ('Lao Ma's Procedural Life', 'Pony's Procedural Life')
t3 = t1 + t2
print(t3)  # (2, 3, 4, 5,'Lao Ma's Procedural Life','Pony's Procedural Life')

summary

So far, the list and tuples are covered. That's all for today! Come on, See You!

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