Introduction to python 06 - Basics of data container (list tuple string) (Part 1)

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1. Introduction

1.1 Transmission above

—⇒Portal: Python Introduction 04-Loop (while and for), variables, function basics

1.2 python column transmission

—⇒ Portal: python basics column

1.2 Types and differences of data containers

Note about the dictionary {k-v}:
key不可以重复 However, if the value
is repeated with any key, it will not report an error ( warning ), but will directly overwrite the previous key.

Container type	Container name	symbol	Whether to modify	Is it in order?	Is it redundant
list	list	[]	yes	yes	yes
gather	set	{}	yes	no	no
string	str	“”	no	yes	yes
tuple	tuple	()	no	yes	yes
dictionary	dict	{“k”:“v”}	yes	no	kno vyes

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2. Basic use of python

2.1 list list <class 'list'>

List element type 不受限制(similar to java's list 不同, also operates on it 不太相似)

• List capacity limit2**63-1
• storable 不同类型elements
• data is 有序stored
• 允许重复数据exist
• 可修改

2.1.1 Definition of list

Introduction to different list definition methods:

-> (1) Same type ( 列表元素type)

lists = ["a", "b", "c"]
print(lists)
# print(type(lists))

-> (2) Different types ( 列表元素types)

lists = ["a", 1, True]
print(lists)
# print(type(lists))

-> (3) Nested list ( 列表元素type)

lists = [["a", 1, True], ["a", 2, False]]
print(lists)
# print(type(lists))

2.1.2 Subscript index of list

下标Search and related operations based on

-> (1) Single-level list (forward subscript)

Look at the abnormal situation:
print(lists[3]) # Error报错: list index out of rangeIndex
subscript is out of range ( Java calls array subscript out of bounds )

lists = ["a", "b", "c"]

print(lists[0])
print(lists[1])
print(lists[2])

-> (2) Single-level list (reverse subscript)

lists = ["a", "b", "c"]

print(lists[-1])
print(lists[-2])
print(lists[-3])

-> (3) Nested list (forward subscript group)

lists1 = [["a", "b", "c"], ["1", "2", "3"]]

print(lists1[0][0])  # a
print(lists1[1][1])  # 2
print(lists1[1][2])  # 3

-> (4) Nested list (reverse subscript group)

lists1 = [["a", "b", "c"], ["1", "2", "3"]]

print(lists1[-1][-1])  # 3
print(lists1[-2][-2])  # b
print(lists1[-2][-3])  # a

2.1.3 Commonly used APIs for lists

For example list, please 先创建listdo the following

lists = ["a", "b", "c"]

->(1) If the subscript corresponding to the searched element does not exist, an error will be reported.

# 查找下表索引 不存在报错
index = lists.index("b")
print(f"b的位置是: {
      
      index}")  # 1

->(2) Modify elements

lists[0] = "a1"
print(lists)

->(3) Insert element

lists.insert(1, "b1")
print(lists)

->(4) Append element (one)

lists.append("d")
print(lists)

->(5) Append 一堆elements

lists2 = [99, 999, 9999]
lists.extend(lists2)
print(lists)

->(6) Delete element ( 四种method)

# 6.1 仅删除元素(根据下标)
del lists[1]
print(lists)

# 6.2 删除元素(等同于 取出下标元素并返回)
lists.pop(0)
print(lists)

# 6.3 删除元素(根据内容 找到第一个元素 删除) 只删除一个
lists.remove("b")
print(lists)

# 6.4 清空列表
lists.clear()
print(lists)

->(7) Count the number of specified elements

lists = ['a', 'a', 'b', 'b', 'c', 'd', 99, 999, 9999]
print(lists.count("a"))  # 2

->(8) Count of all elements in the list

print(len(lists))

->(9) Loop through list elements

while/for循环遍历output
defines two methods

def func_list_while(lists1):
    index = 0
    while index < len(lists1):
        print(lists1[index])
        index += 1


def func_list_for(lists1):
    for index in lists1:
        print(index)

code 测试and 输出results

lists = [1, 2, 3, 4, 5, 6, 7, 8, 9]
func_list_while(lists)
print("上面while循环 下面for循环")
func_list_for(lists)

2.2 Tuple

First look 元组与listat the differences

• list The list can be modified and is []represented by:
• The tuple cannot be modified after it is defined and ()is represented by :tuple()

Application 元组scenarios

• Encapsulate data within the program, and不希望被篡改
• It is somewhat similar to the meaning of java's final modifier.

2.2.1 Define tuples

-> (1) Created under normal circumstances

# 1. 任意类型元素 创建
t1 = (1, "hello", True)
# 2. 空元组定义1
t2 = ()
# 3. 空元组定义2
t3 = tuple()
# 4. 定义一个元素
t4 = tuple("hello")

-> (2) Special circumstances

t6 = ("hello")  

Note: What is represented here is a string.
A hint is given: 让删除括号
the correct way to write it is as follows (two methods)

method one:

t5 = tuple("hello")

Method Two:

t7 = ("hello",)

Overall type query

print(type(t4))
print(type(t5))
print(type(t6))  # <class 'str'> 不加tuple就必须加','
print(type(t7))

-> (3) Nested tuple definition

t8 = ((1, 2, 3), (4, 5, 6))
print(type(t8))
# 输出结果: 6 写法
print(f"嵌套元组下标1,2 的 值是: {
      
      t8[1][2]}")

2.2.2 Commonly used API methods for tuples

First define a t9 tuple

t9 = (1, 2, 3, 3, 5, 6)

-> (1) index() finds the subscript

print(t9.index(2))  # 2元素位置下标是1

-> (2) count() queries the number of specified elements

print(t9.count(3))  # 查看3有几个 2

-> (3) len(element) query tuple length

print(len(t9))  # 查看元组长度 6

2.2.3 Tuple loop traversal

-> (1) while loop

print("\n上面元组语法基础  下面循环 ")
index = 0
while index < len(t9):
    print(t9[index])
    index += 1

-> (2) for loop

for index in t9:
    print(index)

2.2.4 Special cases where tuples can be modified

-> (1) Test whether the tuple can really be modified ( 报错)

t10 = (1, 2, 3, 3, 5, 6)
t10[0] = 999  # TypeError: 'tuple' object does not support item assignment

-> (2) If a list is placed inside, can it be modified ( 可以)

Note: 元组本身cannot be modified
but: the elements inside are 列表[]lists可以修改

t10 = (1, 2, [40, 50, 60])
t10[2][0] = 80
print(t10)  # (1, 2, [80, 50, 60]) 修改成功 元组嵌套的list可修改

2.3 String

String 容器视角interpretation

• support下标索引
• A string is a container of characters. A string can store any number of characters.
• Only strings can be stored and cannot be modified.

2.3.1 String container definition

# 一个字符是一个元素
str1 = "zhangSan is a good boy"

2.3.2 Common APIs for string containers

->(1) index() finds the beginning of the string

value = str1.index("is")
print(value)  # 9

->(2) replace() string replacement

str cannot be modified and a new object will be generated.

str2 = str1.replace("a", "***")
print(str2)  # zh***ngS***n is *** good boy

->(3) split() string splitting

str2 = str1.split(" ")
print(str1)  # zhangSan is a good boy
print(str2)  # ['zhangSan', 'is', 'a', 'good', 'boy']

->(4) strip() string specification

Remove the spaces before and after
strip (element) from front to back 去掉空格并删除第一个元素
java is trim()

str0 = " a b c "
print(str0.strip())  # a b c
print(str0.strip("a "))  # b c 去除空格并删除输入的值(从前到后)

->(5) count() queries the number of occurrences

str1 = "zhangSan is a good boy"
print(str1.count("o"))  # 3

->(6) len() query string length

str1 = "zhangSan is a good boy"
print(len(str1))  # 22

3. Basic grammar summary case

3.1 Basic case of list

3.1.1 Case details

Case Details

1. Declare a list of student ages
2. add an element
3. Add a bunch of elements
4. Take out an age subscript and output it
5. Take out an age subscript backwards and output
6. Find a subscript corresponding to an age Note that an error is reported
7. output the age of any subscript
8. Clear age list

3.1.2 Code implementation

students_age_list = [10, 20, 30, 31, 31, 20]
print(students_age_list)
students_age_list.append(50)
print(students_age_list)
students_age_list.extend([29, 50, 60])
print(students_age_list)
print(students_age_list.pop(0))
print(students_age_list.pop(-1))
print(students_age_list.index(20))
print(students_age_list[0])
print(students_age_list.clear())  # None

4. Summary and preview of the article

4.1 Summary of this article:

• List list defines common operations
• Different common operations between tuples and lists
• Common operations from the string container perspective

4.2 Preview below:

4.2.0 Portal: python column address

4.2.1 Basic 07-Data Container-(sequence slice, collection, dictionary)

4.2.2 Comprehensive case of data containers

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Author pingzhuyan Thanks for watching