day 12 列表字典 补充
1.列表list的遍历
##### while遍历 需要len(list) list = [11,22,33,44,55] len_list = len(list) i = 0 while i<len_list: print(list[i]) i += 1 ###### for 遍历 (不用控制元素的个数,以及下标)推荐 list = [1,2,3,4,5,6,7,8,9] for i in list: print(i)
2.for循环的else (flag)
#### 执行else的语句 list = [11,22,33,44] #list = [] for temp in list: print(temp) else: print("=-===")
#### 不执行else的 break退出 list = [11,22,33,44] #list = [] for temp in list: print(temp) break else: print("=-===")
### flag 版本 card_infors = [{"name":"alex","age":14},{"name":"jack","age":"22"}] find_name = input("请输入你要查找的姓名:") flag = 0 #默认没有找到 for temp in card_infors: if find_name == temp["name"]: flag = 1 print("找到了") if flag == 0: print("查无此人")
##### for else 版本 card_infors = [{"name":"alex","age":14},{"name":"jack","age":"22"}] find_name = input("请输入你要查找的姓名:") for temp in card_infors: if find_name == temp["name"]: print("找到了") break #break,不执行else的语句 else: print("查无此人")
3.列表的append和extend
list1 = [11,22,33,44] list2 = ["a","b"] list1.append(55) print(list1) list1.extend(list2) # extend 俩个 合并 print(list1) list1.append(list2) # append当成一个整体添加 print(list1)
4.list的append的注意点
list1 = [11,22,33] list2 = [44] #list1.append(list2) list1 = list1.append(list2) #list1=None print(list1) #执行结果 None
In [1]: list1 = [11,22,33] In [2]: list1.append(44) #这条命令,执行返回结果 为None #list1 = list1.append(44) 为None In [3]: list1 Out[3]: [11, 22, 33, 44]