Python conditional statements and loops

1. Judgment and Circulation
Python indent
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 = 100while 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 jumps out of the loop
Continue into the next cycle

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 > 5print(l[0:-1])        # 大于等于0     小于5  0 <= a > 5for x,y in enumerate(l):    # 打印列表中元素以及下标    print(x,y)

2, the programming idea is the most important

The most important thing in a programming language is thought.
ABCD Times 9=DCBA, begging for 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))

return Result:
A=1
B=0
C=8
D=9
1089 * 9 = 9801

3. Seeking factorial
To find the factorial of 1-n and
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 totalprint(one(3))status=1while 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))

Python conditional statements and loops