Python条件语句与循环
- 2020 年 1 月 6 日
- 筆記
1、判断与循环 python 缩进 main： print("Hello") print("Hello world.")
if 判断条件: 执行语句 elif 判断条件: 执行语句 else: 执行语句
while 判断条件: 执行语句
a = 100 while a>1: print(a) a-=1 if a==50: break # 退出循环 if a==55: print("5555555555") continue # 此次循环结束，进入下一个循环
break 跳出循环 continue 进入下一次循环
for item in sequence： 执行语句
l = ["a","b","c","d","e","f"] print(l[:]) print(l[0:5]) # 大于等于0 小于5 0 <= a > 5 print(l[0:-1]) # 大于等于0 小于5 0 <= a > 5 for x,y in enumerate(l): # 打印列表中元素以及下标 print(x,y)
2、编程思想最重要
编程语言最重要的是思想 ABCD乘以9=DCBA，求A=？，B=？，C=？，D=？
for A in range(1,10): for B in range(0,10): for C in range(0,10): for D in range(1,10): start = 1000*A+100*B+10*C+D end = 1000*D+100*C+10*B+A if start * 9 == end: print("A={}".format(A)) print("B={}".format(B)) print("C={}".format(C)) print("D={}".format(D)) print("{0} * 9 = {1}".format(start,end))
返回结果： A=1 B=0 C=8 D=9 1089 * 9 = 9801
3、求阶乘 求1-n的阶乘的和 1！+ 2！+ 3！+ 4！+5 ！+ ··· + n！ 0! = 1 1！= 1 2！= 1 2 = 2 3！= 1 2 * 3 = 6
def one(n): total = 1 if n ==0: total = 1 else: for i in range(1,n+1): total *= i return total print(one(3)) status=1 while status: result = 0 n= input("Please input a number(n>=0) : ") for i in n: if not i.isdigit(): print("The number of you input is error.") exit(1) if int(n) < 0: print("The number of you input is error.") break for i in range(0,int(n)+1): result += one(i) print("0! + 1! + 2! + ··· ··· + n! = {}".format(result))
