Python中的while循环，知其然知其所以然

while 条件表达式:
    code1

i = 1
#(2) 写上循环的条件
while i <= 100:

    # (4) 写上循环的逻辑
    print(i)

    # (3) 自增自减的值
    i += 1 # i = i + 1

i = 1
total = 0

#(2) 写上循环的条件
while i <= 100 :
    # (4) 写上自定义的逻辑
    total += i
    # (3) 自增自减的值
    i += 1
print(total)

while True:
    print(1)

i = 1
total = 0
sign = True   #设置个变量，是为了不使用关键字的情况下，控制能退出循环
while sign:
    total += i
    i+=1
    
    # 判断i是否加到了101 , 不参与循环
    if i == 101:
        # 终止循环
        sign = False
print(total) #1 ~ 100 = 5050

help(print)
#help 查看某个方法的文档                相当于linux里面的 --help ，查看某函数(方法)的使用方法
help(print)

i = 0
while i<10:    
    # end='' 打印时,尾部默认不加换行
    print("*",end='')    
    i += 1
# 默认换行
# print()

i = 0
strvar = ""
while i < 10:
    # 写上循环的逻辑
    strvar += "*" # strvar = strvar + "*"
    i +=1
print(strvar)

i = 0
while i < 5:
    print("★☆",end="")
    i+=1

i = 0
while i < 10:
    if i % 2 == 0 :
        print("★",end="")
    else:
        print("☆",end="")
    i+=1

print("<=============>")

i = 0
strvar = ""
while i < 10:
    if i % 2 == 0 :
        strvar += "★"
    else:
        strvar += "☆"
    i+=1
print(strvar)

i = 0 
while i < 100:
    
    # 逻辑写在这里
    print("*" , end="")
    # 打印换行 (在9 19 29 .. 99 )
    if i % 10 == 9:
        print()
    i += 1 

i = 1
while i <= 100:
    
    # 逻辑写在这里
    print("*" , end="")
    # 打印换行 (在10 20 30 .. 100 )
    if i % 10 == 0:
        print()
    i += 1 

i = 0 
while i < 100:
    
    # (1)打印星星
    if i // 10 % 2 == 0:
        print("★",end="")
    else:
        print("☆",end="")

    # (2)打印换行 (在9 19 29 .. 99 )
    if i % 10 == 9:
        print()
    
    i += 1 

i = 10
while i < 110:
    # 打印星星 
    num = int(str(i)[-2])
    if num % 2 == 0 :
        print("★",end="")
    else:
        print("☆",end="")
    # 打印换行
    if i % 10 == 9:
        print()
    i+=1

i = 0
while i < 8:
    j = 0
    while j < 8:
        if i % 2 == 0:
            if j % 2 == 0:
                print("■",end='')
            else:
                print("□", end='')
        else:
            if j % 2 == 1:
                print("■",end='')
            else:
                print("□", end='')
        if j == 7 :
            print()
        j += 1
    i += 1

j = 0 
while j < 10:

    # 打印星星
    i = 0
    while i < 10:
        print("*",end="")
        i+=1
    
    # 打印换行
    print()

    j += 1

i = 0
while i < 10:
    # 打印一行黑白相间的星星
    j = 0
    while j < 10:
        if j % 2 == 0:
            print("☆",end="")
        else:
            print("★",end="")
        j +=1

    # 打印换行
    print()    
    i+=1

i = 0
while i < 10 :
    j = 0
    while j < 10:
        if i % 2 == 0:
            print("☆",end="")
        else:
            print("★",end="")
            
        j +=1
    print()
    i +=1

i = 1
while i <= 9:
    
    # 打印对应的表达式
    j = 1
    while j <= i:
        print("%d*%d=%2d " % (i,j,i*j) ,end="" )
        j+=1
    
    # 打印换行
    print()
    
    i +=1

i = 9
while i >= 1:

    # 打印对应的表达式
    j = 1
    while j <= i:
        print("%d*%d=%2d " % (i,j,i*j) ,end="" )
        j+=1
    
    # 打印换行
    print()

    i -= 1

i = 1
while i <= 9 :
    kongge = 9 - i
    # 打印空格
    while kongge > 0:
        print("       ",end="")
        kongge -= 1  

    # 打印表达式
    j = 1
    while j <= i:
        print("%d*%d=%2d " % (i,j,i*j) ,end="" )
        j+=1
    
    # 换行
    print()
    i +=1

i = 9
while i >= 1 :
    kongge = 9 - i
    # 打印空格
    while kongge > 0:
        print("       ",end="")
        kongge -= 1  

    # 打印表达式
    j = 1
    while j <= i:
        print("%d*%d=%2d " % (i,j,i*j) ,end="" )
        j+=1
    
    # 打印换行
    print()
    i -=1

// 可以获取一个数高位
%  可以获取一个数低位
baiwei = 345 // 100
shiwei = 345 // 10 % 10
gewei  = 345 % 10
print(gewei)

i = 100
while i <= 999:
    baiwei = i // 100
    shiwei = i // 10 % 10
    gewei = i % 10

    if shiwei == gewei  and shiwei == baiwei :
        print(i)
    # 123
    elif shiwei == gewei - 1 and shiwei == baiwei + 1:
        print(i)
    # 987
    elif shiwei == gewei + 1 and shiwei == baiwei - 1:
        print(i)
    i +=1

i = 100
while i <= 999:
    strvar = str(i)
    # print(strvar, type(strvar))
    gewei = int(strvar[-1])
    shiwei = int(strvar[1])
    baiwei = int(strvar[0])
    if shiwei == gewei  and shiwei == baiwei :
        print(i)
    # 123
    elif shiwei == gewei - 1 and shiwei == baiwei + 1:
        print(i)
    # 987
    elif shiwei == gewei + 1 and shiwei == baiwei - 1:
        print(i)
    
    i +=1

i = 100
while i <= 999:
    strvar = str(i)
    # print(strvar, type(strvar))
    gewei = int(strvar[-1])
    shiwei = int(strvar[1])
    baiwei = int(strvar[0])

    if 2 * shiwei == gewei + baiwei and (shiwei == gewei + 1 or shiwei == gewei -1 ):
        print(i)
    elif gewei == shiwei and shiwei == baiwei:
        print(i)
    
    i +=1

x = 0
while x <= 20:
    
    y = 0
    while y <= 33:
        
        z = 0
        while z <= 100:
            
            if x+y+z == 100 and 5*x + 3 * y + 1/3*z == 100 :
                print(x,y,z)
            z += 1    
        
        y +=1
    
    x += 1

if 20 == 20:
    pass
    
while True:
    pass

i = 1
while i <= 10:
    print(i)
    if i == 5:
        break
    i +=1

i = 1
while i <= 10:    
    if i == 5:
        # 在跳过之前,因为会终止执行后面的代码,从下一次循环开始
        # 为了避免死循环,手动加1
        i += 1
        continue
    print(i)
    i +=1

i = 1
while i <= 100:
    strvar = str(i)
    # print(strvar)
    if "4" in strvar:
        i += 1
        continue
    print(i)
    i +=1

i = 1
while i <= 100:
    if i // 10 == 4 or i % 10 == 4:
        i+=1
        continue
    print(i)
    i+=1