Python程序的流程

  1 """
  2 python程序的流程
  3 """
  4 # ------------- 分支结构----------------
  5 # if else
  6 import math
  7 
  8 x = -37
  9 if x < 0:
 10     y = math.fabs(x)
 11 else:
 12     y = math.sqrt(x)
 13 print("计算的结果是：", y)
 14 
 15 # if...elif...else
 16 # month = eval(input("请输入你选择的月份："))  # eval() 函数用来执行一个字符串表达式，并返回表达式的值
 17 month = 12
 18 days = 0
 19 
 20 if (month == 1 or month == 3 or month == 5 or month == 7
 21         or month == 8 or month == 10 or month == 12):
 22     days = 31
 23 elif month == 4 or month == 6 or month == 9 or month == 11:
 24     days = 30
 25 else:
 26     days = 28
 27 print("{}月份的天数为{}".format(month, days))
 28 
 29 # 分支嵌套
 30 flag = 1
 31 books = 8
 32 price = 234
 33 Acp = 0
 34 
 35 if flag == 1:
 36     if books >= 5:
 37         Acp = price * 0.75 * books
 38     else:
 39         Acp = price * 0.85 * books
 40 else:
 41     if books >= 5:
 42         Acp = price * 0.85 * books
 43     else:
 44         Acp = price * 0.95 * books
 45 print("你的实际付款金额是：", Acp)
 46 
 47 # ------------循环结构---------------
 48 
 49 # 遍历循环：for
 50 ‘‘‘
 51 for <var> in <seq>:
 52     <statements>
 53 var是一个变量
 54 seq是一个序列，可以是字符串、列表、文件或range()函数
 55 
 56 range()函数
 57 range(start,stop,[,step])
 58 start：默认从0开始
 59 stop：默认到stop结束，但不包括stop
 60 step：默认为1
 61 ‘‘‘
 62 # 计算1-100中能被3整除数之和
 63 s = 0
 64 for i in range(1, 101, 1):
 65     if i % 3 == 0:
 66         s += i
 67         # print(i)
 68 print(s)
 69 
 70 
 71 # 计算 1！+2！+...+5!
 72 def factorial(n):
 73     t = 1
 74     for v in range(1, n + 1):
 75         t = t * v
 76     return t
 77 
 78 
 79 k = 6
 80 sum1 = 0
 81 for j in range(1, k):
 82     sum1 += factorial(j)
 83 print("1！+2！+...+5!=", sum1)
 84 
 85 # 条件循环语句while
 86 """
 87 while <boolCondition>
 88     <statements>
 89 """
 90 
 91 lst = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
 92 head = 0
 93 tail = len(lst) - 1
 94 while head < len(lst) / 2:  # TypeError: object of type ‘type‘ has no len()/报错，需修改
 95     lst[head], lst[tail] = lst[tail], lst[head]  # 头尾互换?
 96     """
 97     也可以用下面语句来进行头尾互换
 98     temp = list[head]
 99     lst[head] = list[tail]
100     lst[tail] = temp
101     """
102     head += 1
103     tail -= 1
104 
105 for item in lst:
106     print(item, end=‘ ‘)
107 
108 # 用for循环改写
109 lst = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
110 head = 0
111 tail = len(lst) - 1
112 for head in range(0, int(len(lst) / 2)):  # 因为range（）函数的参数必须是整数，所以用int（）函数进行了转换
113     lst[head], lst[tail] = lst[tail], lst[head]  # 头尾互换?
114     """
115     也可以用下面语句来进行头尾互换
116     temp = list[head]
117     lst[head] = list[tail]
118     lst[tail] = temp
119     """
120     head += 1
121     tail -= 1
122 
123 for item in lst:
124     print(item, end=‘ ‘)
125 print()
126 
127 # ------------跳转语句----------------
128 """
129 break语句的作用是从循环体内跳出，及结束循环
130 """
131 a = 99
132 i = a // 2
133 while i > 0:
134     if a % i == 0:
135         break
136     i -= 1
137 print(a, "的最大真约数：", i)
138 
139 """
140 continue语句必须用于循环结构中，它的作用是终止当前的这一轮循环，跳过本轮剩余的语句，直接进入下一循环
141 """
142 s = [-1, -2, -3, -4, 5, 6, 7, 8, 9]
143 for i in range(9):
144     if s[i] < 0:
145         continue
146     print("{}是正数".format(s[i]))
147 
148 # 打印金字塔
149 # n = eval(input("请输入打印的行数"))
150 n = 5
151 for i in range(1, n + 1):
152     print(‘ ‘ * (n - i) + ‘*‘ * (2 * i - 1))  # 感觉这个print函数都够学的了