一.if 判断
代码段
user = 'joy' password = '123456' # 输入用户名和密码 user_account = input('please input user:') user_password = input('please input password:')
# 判断用户名和密码是否正确 if user == user_account and password == user_password : print('登录成功') else: print('用户名或密码错误')
输出结果
please input user:abb please input password:2387 用户名或密码错误
二.elif 多分支
代码段A (使用 if + else 实现)
result = int(input("你的成绩是:")) if result > 80 and result <= 100 : print("优秀成绩") else : if result <= 80 and result >= 60 : print("中等成绩") else: if result < 60 : print("成绩较差") else : print("成绩异常")
代码段B (使用 if + elif + else 实现)
result = int(input("你的成绩是:")) # input默认为str类型,需要转换成int类型 if result > 80 and result <= 100 : print("优秀成绩") elif result <= 80 and result >= 60 : print("中等成绩") elif result < 60 : print("成绩较差") else : print("成绩异常")
输出结果
你的成绩是:65 中等成绩
三.while 循环
代码段
# while 递归 a = 1 c = 1 while a <= 100 : b = 0 while b <= 9 : b += 1 print(a,end=" ") # 打印一个数字,end留一个空格 a += 1 print("".strip(" ")) # strip去除字符串首位转义字符,换行、空格 else : print("end")
输出结果
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 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 end
四.for 循环
主要用来遍历、循环、序列或者集合、字典
代码段
goods = [['ipad','iphone','iwatch','imacbook','headphone'],(4800,6500,3200,150000,2400)] for i in goods: for x in i: print(x,end=" ") else: print('fruit is gone')
输出结果
ipad iphone iwatch imacbook headphone 4800 6500 3200 150000 2400 fruit is gone
1.break 跳出
代码段
goods = ['ipad','iphone','iwatch','imacbook','headphone'] for i in goods: if i == 'iwatch': break # 跳出,终止程序 print(i)
输出结果
ipad iphone
2.continue 跳过、继续
代码段
goods = ['ipad','iphone','iwatch','imacbook','headphone'] for i in goods: if i == 'iwatch': continue # 跳过,继续 print(i)
输出结果
ipad iphone imacbook headphone
3.嵌套循环
代码段
goods = [['ipad','iphone','iwatch','imacbook','headphone'],(4800,6500,3200,150000,2400)] for i in goods: # print(i) for x in i: # print(x) if x == 'iwatch': break # break只会影响同一级的for循环,其他for循环正常运行 print(x,end=" ") else: print('fruit is gone')
输出结果
ipad iphone imacbook headphone ipad iphone 4800 6500 3200 150000 2400 fruit is gone
4.阵列
代码段
for x in range(2,101,2): print(x,end='|') print(" ") for y in range(100,1,-2): # 倒序 print(y,end='|')
输出结果
2|4|6|8|10|12|14|16|18|20|22|24|26|28|30|32|34|36|38|40|42|44|46|48|50|52|54|56|58|60|62|64|66|68|70|72|74|76|78|80|82|84|86|88|90|92|94|96|98|100| 100|98|96|94|92|90|88|86|84|82|80|78|76|74|72|70|68|66|64|62|60|58|56|54|52|50|48|46|44|42|40|38|36|34|32|30|28|26|24|22|20|18|16|14|12|10|8|6|4|2|
5.列表阵列
代码段
number = [1,2,3,4,5,6,7,8,9,10] for a in number[0:len(number):2]: # 方法一:使用切片 print(a,end=' ') print(" ") for b in range(1,len(number),2): # 方法二:使用range方法 print(b,end=' ')
输出结果
1 3 5 7 9 1 3 5 7 9
number = [1,2,3,4,5,6,7,8,9,10]
for a in number[0:len(number):2]: # 方法一:使用切片
print(a,end=' ')
print("
")
for b in range(1,len(number),2): # 方法二:使用range方法
print(b,end=' ')