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