python 基础之第三天

例子1：8位数的随机密码

 #!/usr/bin/python
 # coding:utf-8

 import string
 import random

 pwd = ''
 for i in range(8):
     char = random.choice(string.printable)
     pwd += char

 print pwd

验证：

 [root@master script]# python ranpass.py
 9W3HXhrI

改进版：

 #!/usr/bin/python
 # coding:utf-8

 import string
 import random
 import sys

 def get_pass(num):
     pwd = ''
     for i in range(num):
          char = random.choice(string.printable)
          pwd += char
     return pwd
 if __name__ == '__main__':
     print get_pass(int(sys.argv[1]))

备注：

In [3]: string.printable
Out[3]: '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!"#$%&\'()*+,-./:;<=>?@[\\]^_`{|}~ \t\n\r\x0b\x0c'

a和b 的值互换：

 In [18]: a = 10

 In [19]: b = 20

 In [20]: a,b = b,a

 In [21]: a
 Out[21]: 20

 In [22]: b
 Out[22]: 10

程序例子：

创建一个文件，判断文件是否存在，不存在则创建，存在则直接写入数据

关键词：import os ; os.path.isfile('/etc/passwd')  用于判断文件是否存在

os.path.isdir('/etc/') 用于判断目录是否存在

#!/usr/bin/python
# coding:utf-8

import os
contents = []
while True:
    fname = raw_input('filename: ')
    if not os.path.exists(fname):
        break
    print '%s already exists,Try again' % fname

while True:
    data = raw_input('<Enter to quit>: ')
    if not data:
        break
    contents.append(data + '\n')

f = open(fname,'w')
f.writelines(contents)
f.close()

通过函数的改进版：

 #!/usr/bin/python
 # coding:utf-8

 import os
 def file_name():
     while True:
         fname = raw_input('filename: ')
         if not os.path.exists(fname):
             break
         print '%s already exists,Try again' % fname
     return fname
 def content():
     contents = []
     while True:
         data = raw_input('<Enter to quit>: ')
         if not data:
             break
         contents.append(data + '\n')
     return contents
 def wfile(fname,contents):
     f = open(fname,'w')
     f.writelines(contents)
     f.close()

 if __name__ == '__main__':
     wfile(file_name(),content())

##############如何查看python的关键字有哪些#################

In [32]: import keyword
In [33]: keyword.kwlist
Out[33]:
['and',
 'as',
 'assert',
 'break',
 'class',
 'continue',
 'def',
 'del',
 'elif',
 'else',
 'except',
 'exec',
 'finally',
 'for',
 'from',
 'global',
 'if',
 'import',
 'in',
 'is',
 'lambda',
 'not',
 'or',
 'pass',
 'print',
 'raise',
 'return',
 'try',
 'while',
 'with',
 'yield']

In [34]: keyword.iskeyword('def')
Out[34]: True