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一篇文章带你学习Python3的高级特性(1)

目录
  • 1.切片
  • 2.迭代
  • 3.列表生成式
  • 总结

1.切片

# 切片:取list或tuple的部分元素
nameList = ["Willard","ChenJD","ChenBao","ChenXiaoBao","hackerLuo"]
print("nameList的内容为:",nameList)
print("------------------------------------------------------------------------------")
# 传统方法取nameList前三个元素
print("nameList前三个元素:",[nameList[0],nameList[1],nameList[2]])
print("------------------------------------------------------------------------------")
# 使用切片取前三个元素,注:切片也是左闭右开
print("使用切片操作取nameList前三个元素:",nameList[0:3])
print("使用切片操作取nameList第二个到第四个元素:",nameList[1:5])
print("------------------------------------------------------------------------------")
print("------------------------------------------------------------------------------")
# 切片的一些常用操作
numsList = list(range(30))
print("数字列表内容为:\n",numsList)
print("------------------------------------------------------------------------------")
print("数字列表前10个数内容:",numsList[0:10])
print("数字列表前10个数内容:",numsList[:10])
print("\n")
print("数字列表后10个数内容:",numsList[-10:])
print("数字列表编程客栈前11-20个数内容:",numsList[10:20])
print("数字列表前10个数每隔两wXJcZLpE个取一个:",numsList[0:10:2])
print("数字列表前10个数每隔两个取一个:",numsList[:10:2])
print("数字列表每隔3个数取一个:",numsList[::3])
print("数字列表内容:\n",numsList[:])
# Tips:
# 1.tuple可以使用切片操作,操作的结果仍是tuple;
# (0,1,2,3,4,5)[:3]  ===>  (0,1,2)
# 2.字符串使用切片操作,一个字符就是一个元素
# "Welcome to FUXI Technology."[:3]  ===>  "Wel"

# 结果输出:

nameList的内容为: ['Willard', 'ChenJD', 'ChenBao', 'ChenXiaoBao', 'hackerLuo']

------------------------------------------------------------------------------

nameList前三个元素: ['Willard', 'ChenJD', 'ChenBao']

------------------------------------------------------------------------------

使用切片操作取nameList前三个元素: ['Willard', 'ChenJD', 'ChenBao']

使用切片操作取nameList第二个到第四个元素: ['ChenJD', 'ChenBao', 'ChenXiaoBao', 'hackerLuo']

------------------------------------------------------------------------------

------------------------------------------------------------------------------

数字列表内容为:

 [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29]

------------------------------------------------------------------------------

数字列表前10个数内容: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

数字列表前10个数内容: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

数字列表后10个数内容: [20, 21, 22, 23, 24, 25, 26, 27, 28, 29]

数字列表前11-20个数内容: [10, 11, 12, 13, 14, 15, 16, 17, 18, 19]

数字列表前10个数每隔两个取一个: [0, 2, 4, 6, 8]

数字列表前10个数每隔两个取一个: [0, 2, 4, 6, 8]

数字列表每隔3个数取一个: [0, 3, 6, 9, 12, 15, 18, 21, 24, 27]

数字列表内容:

 [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20编程客栈, 21, 22, 23, 24, 25, 26, 27, 28, 29]

 

2.迭代

# 给定一个list或tuple,通过for循环来遍历这个list或tuple,这种遍历称为迭代(iteration);# 迭代通过for...in来完成;# 实例1:迭代dictpersonInfoDict = {"name":"Willard","age":18,"job":"Engineer"}print("使用迭代读取dict内容!")print("personInfoDict的内容:",personInfoDict)print("------------------------------------------------------------------------------")# 读取personInfoDict的key值print("personInfoDict的key值:")for key in personInfoDict:    print(key,end = " ")print("\n")print("personInfoDict的value值:")for value in personInfoDict.values():    print(value,end = " ")    print("\n")print("personInfoDict的key-value值:")for item in personInfoDict.items():    print(item,end = " ")print("\n")print("------------------------------------------------------------------------------")print("------------------------------------------------------------------------------")# 实例2:迭代读取字符串userNameStr = "WillardLuo"print("使用迭代读取字符串内容!")print("userNameStr的内容:",userNameStr)print("------------------------------------------------------------------------------")print("userNameStr的每个元素为:")for word in userNameStr:    print(word,end = " ")# 给定一个list或tuple,通过for循环来遍历这个list或tuple,这种遍历称为迭代(iteration);
# 迭代通过for...in来完成;
# 实例1:迭代dict
personInfoDict = {"name":"Willard","age":18,"job":"Engineer"}
print("使用迭代读取dict内容!")
print("personInfoDict的内容:",personInfoDict)
print("------------------------------------------------------------------------------")
# 读取personInfoDict的key值
print("personInfoDict的key值:")
for key in personInfoDict:
    print(key,end = " ")
print("\n")
print("personInfoDict的value值:")
for value in personInfoDict.values():
    print(value,end = " ")
print("\n")
print("personInfoDict的key-value值:")
for item in personInfoDict.items():
    print(item,end = " ")
print("\n")
print("------------------------------------------------------------------------------")
print("------------------------------------------------------------------------------")
# 实例2:迭代读取字符串
userNameStr = "WillardLuo"
print("使用迭代读取字符串内容!")
print("userNameStr的内容:",userNameStr)
print("------------------------------------------------------------------------------")
print("userNameStr的每个元素为:")
for word in userNameStr:
    print(word,end = " ")

# 结果输出:

使用迭代读取dict内容!

personInfoDict的内容: {'name': 'Willard', 'age': 18, 'job': 'Engineer'}

------------------------------------------------------------------------------

personInfoDict的key值:

name age job 

personInfoDict的value值:

Willard 18 Engineer 

personInfoDict的key-value值:

('name', 'Willard') ('age', 18) ('job', 'Engineer') 

------------------------------------------------------------------------------

------------------------------------------------------------------------------

使用迭代读取字符串内容!

userNameStr的内容: WillardLuo

------------------------------------------------------------------------------

userNameStr的每个元素为:

W i l l a r d L u o  

# Tips:
# 1.使用for...in循环需要作用于一个可迭代对象;
# 2.判断一个对象是否是可迭代对象,可通过collections.abs模块的Iterable类型判断
from collections.abc import Iterable
nameStr = "WillardLuo"
nameList = ["Willard","ChenJD","ChenBao"]
numberTuple = (1,2,3,4,5)
personInfoDict = {"name":"Willard","age":18}
number = 100
print("判断字符串是否是可迭代对象!")
print(isinstance(nameStr,Iterable))
print("判断列表是否是可迭代对象!")
print(isinstance(nameList,Iterable))
print("判断元组是否是可迭代对象!")
print(isinstance(numberTuple,Iterable))
print("判断字典是否是可迭代对象!")
print(isinstance(personInfoDict,Iterable))
print("判断数字是否是可迭代对象!")
print(isinstance(number,Iterable))
print("------------------------------------------------------------------------------")
print("------------------------------------------------------------------------------")
# 实现对list进行下标循环
# 使用enumerate函数把一个list变成"索引-元素"对
nameList = ["Willard","ChenJD","ChenBao","ChenXiaoBao","hackerLuo"]
for index,value in enumerate(nameList):
    print(index,value)
    
print("------------------------------------------------------------------------------")
willardInfo = {"name":"Willard","age":18,"job":"Engineer"}
# 循环中同时引用两个变量,数据处理中常用
for key,value in willardInfo.items():
    print(key,value)

# 结果输出:

判断字符串是否是可迭代对象!

True

判断列表是否是可迭代对象!

True

判断元组是否是可迭代对象!

True

判断字典是否是可迭代对象!

True

判断数字是否是可迭代对象!

False

------------------------------------------------------------------------------

------------------------------------------------------------------------------

0 Willard

1 ChenJD

2 ChenBao

3 ChenXiaoBao

4 hackerLuo

------------------------------------------------------------------------------

name Willard

age 18

job Engineer

 

3.列表生成式

# 列表生成式:List Comprehensions,用来创建list的生成式
# 实例1:生成[11,22,33,...,1010]的列表
# 法一:循环
numsList = []
for num in range(1,11):
    numsList.append(num * num)
print("numsList的内容:",numsList)
print("---------------------------------------------------------")
# 法二:列表生成式
print("列表生成式生成上述列表!")
# 把要生成的元素放在前面,后面加循环
print([num * num for num in range(1,11)])
print("---------------------------------------------------------")
# 在循环后添加if判断,筛选1-10中偶数的平方
print("列表生成式生成1-10偶数的平方的列表")
print([num * num for num in range(1http://www.cppcns.com,11) if num % 2 == 0])
print("---------------------------------------------------------")
# 双重循环
print("列表生成式应用于双重循环")
print([m + n for m in "Willard" for n in "ChenJD"])

# 结果输出:

numsList的内容: [1, 4, 9, 16, 25, 36, 49, 64, 81, 100]

---------------------------------------------------------

列表生成式生成上述列表!

[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]

---------------------------------------------------------

列表生成式生成1-10偶数的平方的列表

[4, 16, 36, 64, 100]

---------------------------------------------------------

列表生成式应用于双重循环

[&#www.cppcns.com39;WC', 'Wh', 'We', 'Wn', 'WJ', 'WD', 'iC', 'ih', 'ie', 'in', 'iJ', 'iD', 'lC', 'lh', 'le', 'ln', 'lJ', 'lD', 'lC', 'lh', 'le', 'ln', 'lJ', 'lD', 'aC', 'ah', 'ae', 'an', 'aJ', 'aD', 'rC', 'rh', 're', 'rn', 'rJ', 'rD', 'dC', 'dh', 'de', 'dn', 'dJ', 'dD']

 

总结

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