Python及爬虫学习.zip

# -*- encoding: utf-8 -*- """ @File : python_test.py @Modify Time : 2023/12/30 22:36 @Author : Allen.Yang @Contact : MC36514@um.edu.mo @Description : 介绍Python基础知识 """ # 变量 float_variable = 1.0 # 浮点型 int_variable = 1 # 整形 string_variable = "Hello, i am fine." print(f"float_variable 是:{float_variable}, int_variable 是:{int_variable}，二者相加结果是:{float_variable+int_variable}") # 字符串运算 str_original = "I come from China." # 空格也算字符，会占位 # 最大取值范围不包括该值 # 第三个参数代表步长step，可以省略 print(str_original[1:5:2]) print(str_original[-5:-1]) str_original_2 = "What about u?" # 字符串相关操作 print(str_original + str_original_2) print(str_original * 2) print("*" in str_original) print("I" in str_original) # 字符串函数操作 # 统计子字符串在原字符串中出现次数 print(str_original.count("come")) print(str_original.find("me")) print(len(str_original)) print(str_original.upper()) print(str_original.replace("come","coooool")) print(str_original.split(" ")) # 列表 list_A = ['i','am',123,[1,2,3]] print(list_A) print(list_A * 3) print([1,2] * 3) print( 3 in [1,2,3]) for x in [1,2,3]: print(x,end=" ") print() # 列表操作函数 # 列表末尾添加对象 list_A.append("1") print(list_A) # 统计某个元素在列表中出现的次数 print(list_A.count(123)) # 在列表中扩展另一个列表中的元素 list_A.extend([1,2,3]) print(list_A) # 从列表中找出某一个值第一个匹配项索引的位置 print(list_A.index(1)) # 将对象插入列表 list_A.insert(0,"Yang") print(list_A) # 弹出列表元素 pop_value = list_A.pop(2) print(pop_value) print(list_A) # 排序 list_string = ['a','cb','ca'] list_string.sort() print(list_string) list_num = [3,2,5,7,9] list_num.reverse() print(list_num) list_num.sort(reverse=False) print(list_num) list_num.sort(reverse=True) print(list_num) # 字典变量 # 字典形式为 key=>value，键:值 dict_lastName = {1:"Yang",2:"Wang",3:"Yu",'haha':"Kong",5:"Zhao"} dict_lastName[100] = 'Cat' print(dict_lastName['haha']) dict_lastName['haha'] = "123456" print(dict_lastName) # 删除键 del dict_lastName[1] print(dict_lastName) # 打包创建字典 dict_test = {} list_key = ['name','phone','address'] list_value = ['Allen',123,'China'] key_value_pairs = zip(list_key,list_value) dict_result = dict(key_value_pairs) print(dict_result) # get返回值,找到name1键则返回name1键对应的值，不然返回后面的默认值 print(dict_result.get('name1',"aaa")) # 删除字典里的值 item = dict_result.pop('name') print(item) print(dict_result) # match case 用法 status = 40 match status: case 400: print("status is 400") case 401: print("status is 401") case 402: print("status is 402") case 403: print("status is 403") case _: print("wrong") # while else用法 count = 0 while count < 5: print (count, " 小于 5") count = count + 1 else: print (count, " 大于或等于 5") # for else用法 for x in range(6): print(x) else: print("Finally finished!") # break和continue # break直接跳出所有循环 # continue只跳过当前轮次，继续进行后续的循环 n = 5 while n > 0: n -= 1 if n == 2: break print(n) print('循环结束。') n = 5 while n > 0: n -= 1 if n == 2: continue print(n) print('循环结束。') # 推导式 names = ['Bob','Tom','alice','Jerry','Wendy','Smith'] new_names = [name.upper() for name in names if len(name)>3 and name != 'Jerry'] print(new_names) dic = {x: x**2 for x in (2, 4, 6)} print(dic) # 函数，返回更大的值 # 这里面的a,b是形式参数 def max(a, b): if a > b: return a else: return b num1 = 4 num2 = 5 print(max(num1, num2)) # lambda表达式，lambda 参数1,参数2: 运算 x = lambda a, b : a * b print(x(5, 6)) # map联用，对列表里每一个元素应用函数运算 numbers = [1, 2, 3, 4, 5] squared = list(map(lambda x: x**2, numbers)) print(squared) # filter过滤 numbers = [1, 2, 3, 4, 5, 6, 7, 8] even_numbers = list(filter(lambda x: x % 2 == 0, numbers)) print(even_numbers) # reduce对list元素进行累计计算 from functools import reduce numbers = [1, 2, 3, 4, 5] product = reduce(lambda x, y: x * y, numbers) print(product)