html,body,div,span,applet,object,iframe,h1,h2,h3,h4,h5,h6,p,blockquote,pre,a,abbr,acronym,address,big,cite,code,del,dfn,em,img,ins,kbd,q,s,samp,small,strike,strong,sub,sup,tt,var,b,u,i,center,dl,dt,dd,ol,ul,li,fieldset,form,label,legend,table,caption,tbody,tfoot,thead,tr,th,td,article,aside,canvas,details,embed,figure,figcaption,footer,header,hgroup,menu,nav,output,ruby,section,summary,time,mark,audio,video { margin: 0; padding: 0; border: 0 }
body { font-family: Helvetica, arial, freesans, clean, sans-serif; font-size: 14px; line-height: 1.6; color: #333; background-color: #fff; padding: 20px; max-width: 960px; margin: 0 auto }
body>*:first-child { margin-top: 0 !important }
body>*:last-child { margin-bottom: 0 !important }
p,blockquote,ul,ol,dl,table,pre { margin: 15px 0 }
h1,h2,h3,h4,h5,h6 { margin: 20px 0 10px; padding: 0; font-weight: bold }
h1 tt,h1 code,h2 tt,h2 code,h3 tt,h3 code,h4 tt,h4 code,h5 tt,h5 code,h6 tt,h6 code { font-size: inherit }
h1 { font-size: 28px; color: #000 }
h2 { font-size: 24px; border-bottom: 1px solid #ccc; color: #000 }
h3 { font-size: 18px }
h4 { font-size: 16px }
h5 { font-size: 14px }
h6 { color: #777; font-size: 14px }
body>h2:first-child,body>h1:first-child,body>h1:first-child+h2,body>h3:first-child,body>h4:first-child,body>h5:first-child,body>h6:first-child { margin-top: 0; padding-top: 0 }
a:first-child h1,a:first-child h2,a:first-child h3,a:first-child h4,a:first-child h5,a:first-child h6 { margin-top: 0; padding-top: 0 }
h1+p,h2+p,h3+p,h4+p,h5+p,h6+p { margin-top: 10px }
a { color: #4183C4; text-decoration: none }
a:hover { text-decoration: underline }
ul,ol { padding-left: 30px }
ul li>:first-child,ol li>:first-child,ul li ul:first-of-type,ol li ol:first-of-type,ul li ol:first-of-type,ol li ul:first-of-type { margin-top: 0px }
ul ul,ul ol,ol ol,ol ul { margin-bottom: 0 }
dl { padding: 0 }
dl dt { font-size: 14px; font-weight: bold; font-style: italic; padding: 0; margin: 15px 0 5px }
dl dt:first-child { padding: 0 }
dl dt>:first-child { margin-top: 0px }
dl dt>:last-child { margin-bottom: 0px }
dl dd { margin: 0 0 15px; padding: 0 15px }
dl dd>:first-child { margin-top: 0px }
dl dd>:last-child { margin-bottom: 0px }
pre,code,tt { font-size: 12px; font-family: Consolas, "Liberation Mono", Courier, monospace }
code,tt { margin: 0 0px; padding: 0px 0px; white-space: nowrap; border: 1px solid #eaeaea; background-color: #f8f8f8 }
pre>code { margin: 0; padding: 0; white-space: pre; border: none; background: transparent }
pre { background-color: #f8f8f8; border: 1px solid #ccc; font-size: 13px; line-height: 19px; overflow: auto; padding: 6px 10px }
pre code,pre tt { background-color: transparent; border: none }
kbd { background-color: #DDDDDD; background-image: linear-gradient(#F1F1F1, #DDDDDD); background-repeat: repeat-x; border-color: #DDDDDD #CCCCCC #CCCCCC #DDDDDD; border-style: solid; border-width: 1px; font-family: "Helvetica Neue", Helvetica, Arial, sans-serif; line-height: 10px; padding: 1px 4px }
blockquote { border-left: 4px solid #DDD; padding: 0 15px; color: #777 }
blockquote>:first-child { margin-top: 0px }
blockquote>:last-child { margin-bottom: 0px }
hr { clear: both; margin: 15px 0; height: 0px; overflow: hidden; border: none; background: transparent; border-bottom: 4px solid #ddd; padding: 0 }
table th { font-weight: bold }
table th,table td { border: 1px solid #ccc; padding: 6px 13px }
table tr { border-top: 1px solid #ccc; background-color: #fff }
table tr:nth-child(2n) { background-color: #f8f8f8 }
img { max-width: 100% }

内存管理： python 变量重新赋值之后，对应的内存地址会变

引用计数

del是解除绑定

内存地址复用

>>> x=1
>>> id(x)
9310240
>>> x=2
>>> id(x)
9310272
>>> y=1
>>> id(y)
9310240

字符串格式化控制符

print(‘用户名是： %s 密码是： %s‘ %)

使用while循环打印1 2 3 4 5 6 8 9 10

x = 1
print(‘Now, Print the numbers: ‘, end=‘ ‘)
while x < 11:
    print(x, end=‘ ‘)
    if x == 6:
        x += 2
        print("  ", end=‘‘)
    else:
        x += 1

方法二

print(‘\n‘)
x = 0
while x < 10:
    x += 1
    if x == 7:
        continue
    print(x, end=‘ ‘)

求1-100的和

print(‘\n‘)
y = 1
sum = 0
while y < 101:
    sum += y
    y += 1
print(‘1-100的所有数的和是：‘, sum)

print(‘\n‘)

求 1-100内所有的偶数

print(‘100以内所有的偶数： ‘, end=‘‘)
for i in range(1, 101):
    if i % 2 == 0:
        print(i, end=‘ ‘)

求100以内的奇数

print(‘\n‘)
print(‘100以内所有的奇数： ‘, end=‘ ‘)
for ii in range(1, 101):
    if ii % 2 != 0:
        print(ii, end=‘ ‘)

print(‘\n‘)

求1-2+3-4+5 ... 99的所有数的和

sum = 0
for i in range(1, 100):
    if i % 2 == 0:
        sum -= i
        print(‘-‘, i, end=‘‘)
    else:
        sum += i
        print(‘+‘, i, end=‘‘)
print(‘=‘, sum)

用户登陆（三次机会重试）

username = (‘cx2c‘)
password = (‘cx2c‘)
for i in range(1,4):
    user=input(‘Please Input Your Name: ‘)
    pasw=input(‘Please Input Your Password: ‘)
    if username == user and password==pasw:
        print(‘Login in successful‘)
        break
    else:
        print(‘The %sth time False,Try Again‘ %i)

打印结果

Now, Print the numbers:  1 2 3 4 5 6   8 9 10 

1 2 3 4 5 6 8 9 10 

1-100的所有数的和是： 5050

100以内所有的偶数： 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以内所有的奇数：  1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 71 73 75 77 79 81 83 85 87 89 91 93 95 97 99 

+ 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= 50
Please Input Your Name: cx2c
Please Input Your Password: cc
False
Please Input Your Name: cx2c
Please Input Your Password: cx2c
Login in successful