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python的介绍

python2与3的区别

Old: print "The answer is", 2*2

New: print ("The answer is", 2*2)

Old:

New:

windows添加python2.7 和3.5环境变量

##2.7

##3.5

##python.exe 重命名为python35.exe

centos 6.6安装python2.7和3.5

yum groupinstall 'Development Tools'

tar xf Python-3.5.0.tgz

cd Python-3.5.0

./configure --prefix=/usr/local/python3

make all

make install

echo $?

make clean

make distclean

安装步骤如下：
1 准备编译环境(环境如果不对的话，可能遇到各种问题，比如wget无法下载https链接的文件)

yum groupinstall 'Development Tools'

yum install zlib-devel bzip2-devel openssl-devel ncurses-devel

2 下载 Python3.5代码包

wget https://www.python.org/ftp/python/3.5.0/Python-3.5.0.tar.xz

3 编译

tar Jxvf Python-3.5.0.tar.xz

cd Python-3.5.0

./configure --prefix=/usr/local/python3

make && make install

4.此时，新版本的python没有覆盖原来的版本，先将原来的python重命名

# mv /usr/bin/python /usr/bin/python_old

5 替换系统默认的2.6版本的python

ln -sv /usr/local/python3/bin/python3.5 /usr/bin/python

##这样做的目的是在系统任意目录敲入python调用的是python3的命令，而非系统默认2.6.6的

但是这样同时这会导致依赖python2.6的yum不能使用，因此还要修改yum配置。

6 更新yum配置。

vim /usr/bin/yum

通过vim修改yum的配置

#!/usr/bin/python

改为

#!/usr/bin/python2.6

保存退出。完成了python3的安装。

7 安装pip

pip是根据官网wiki安装的。
1，安装setuptools。pip安装前需要先安装setuptools，在上面的页面中给出了下载地址。下载并执行即可：

wget https://pypi.python.org/packages/source/s/setuptools/setuptools-5.7.zip --no-check-certificate

unzip setuptools-5.7.zip

cd setuptools-5.7

python setup.py install

wget https://pypi.python.org/packages/source/p/pip/pip-7.1.2.tar.gz#md5=3823d2343d9f3aaab21cf9c917710196

tar xvf pip-7.1.2.tar.gz

cd pip-7.1.2

python setup.py install

OK 大功告成

python简单示例

1.变量,字符集,头文件

变量定义的规则

定义字符集

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Author: liwx

#..最多不能超过80个字符每行...

自动添加头文件

2.菜单内引用变量

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Author: liwx

name = input("input your name:")
age = int(input("input your age:") )
job = input("input your job:")

msg = '''
Infomation of user %s:
-------------------
Name: %s
Age : %f
Job : %s
--------END--------
''' % (name,name,age,job)

print(msg)

执行结果

[root@liwx python]# python caidan_bianliang.py

input your name:liwx

input your age:28

input your job:IT

infomation of user liwx:

---------------------------

name: liwx

age : 28

job : IT

--------------END----------

导入模块

getpass-密文

[root@liwx python]# vim 2.py

import getpass

username = input("please input username:")

passwd = getpass.getpass("please input passwd:")

print(username,passwd)

执行结果(密码看不见,是密文)

OS-inux命令模块

[root@liwx python]# cat 3.py

import os

os.system("ls")

os.system("df -h")

os.mkdir("/root/1234444")

print ("---------------------")

os.system("ls /root/")

结果

[root@liwx python]# python 3.py

2.py 3.py caidan_bianliang.py

Filesystem Size Used Avail Use% Mounted on

/dev/sda3 7.1G 1.8G 5.0G 26% /

tmpfs 242M 0 242M 0% /dev/shm

/dev/sda1 190M 27M 153M 15% /boot

---------------------

123 install.log.syslog setuptools-5.7

1234444 nux-dextop-release-0-2.el6.nux.noarch.rpm setuptools-5.7.zip

anaconda-ks.cfg Python-3.5.0 youhua.sh

install.log Python-3.5.0.tgz

把返回的结果赋值给变量

>>> cmd_res = os.popen("df -h").read()

>>> print cmd_res

Filesystem Size Used Avail Use% Mounted on

/dev/sda3 7.1G 1.4G 5.4G 21% /

tmpfs 242M 0 242M 0% /dev/shm

/dev/sda1 190M 27M 153M 15% /boot

>>> print(cmd_res)

Filesystem Size Used Avail Use% Mounted on

/dev/sda3 7.1G 1.4G 5.4G 21% /

tmpfs 242M 0 242M 0% /dev/shm

/dev/sda1 190M 27M 153M 15% /boot

3.tab.py环境变量模块

##查看python的环境变量

>>> import sys

>>> print(sys.path)

['', '/usr/lib64/python26.zip', '/usr/lib64/python2.6', '/usr/lib64/python2.6/plat-linux2', '/usr/lib64/python2.6/lib-tk', '/usr/lib64/python2.6/lib-old', '/usr/lib64/python2.6/lib-dynload', '/usr/lib64/python2.6/site-packages', '/usr/lib/python2.6/site-packages']

Tab 补全

#!/usr/bin/env python

# python startup file

import sys

import readline

import rlcompleter

import atexit

import os

# tab completion

readline.parse_and_bind('tab: complete')

# history file

histfile = os.path.join(os.environ['HOME'], '.pythonhistory')

try:

readline.read_history_file(histfile)

except IOError:

pass

atexit.register(readline.write_history_file, histfile)

del os, histfile, readline, rlcompleter

>>> import tab.py

Traceback (most recent call last):

File "<stdin>", line 1, in <module>

File "/usr/local/python3/lib/python3.5/site-packages/tab.py", line 4, in <module>

import readline

ImportError: No module named 'readline

if 判断

user = "liwx"

passwd = "liwx123"

username = raw_input("username:")

password = raw_input("passwd:")

if user == username:

print("username is OK")

if passwd == password:

print("Welcome login .....")

else:

print("passwd is NONONO")

else:

print("username is NONONONO")

优化版

[root@liwx ~]# python if_user.py

username:liwx

passwd:liwx123

username is OK

Welcome login .....

[root@liwx ~]# python if_user.py

username:liwx

passwd:sfdsf

username is OK

passwd is NONONO

[root@liwx ~]# python if_user.py

username:sdf

passwd:sdf

username is NONONONO

猜年龄

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Author: liwx

age = 22
counter = 0
for i in range(10):
if counter <3:
guess_num = int(input("input your guess num:"))
if guess_num == age:
print("you guess is OK")
break #跳出整个循环
elif guess_num > age:
print("you guess is big")
else:
print("you guess is small")
else:
please_confirm = input("NUM > 3,do you want continue (y/n) :")
if please_confirm == 'y':
counter = 0
continue #跳出当次循环,不计数
else:
print("bye bye")
break
counter += 1 #counter = counter + 1