recently encountered an error using python to unzip rar.
installation is the rarfile package, but the implementation of decompression error, the Internet to find a lot of methods have not solved.

import rarfile
path1 = "E://test.rar"
with rarfile.RarFile(path1) as rf:
    rf.extractall()

currently the main online solutions are as follows:
1. Put winrar. Exe under python project venv – scripts. 2. Install unrar on Windows and configure environment variables.

I tried the first method and found that it did not solve the problem, and I did not try the second method because I could not find a suitable installation package.

considering that winrar program is installed on the machine, so inspired by the second method, configure winrar path in the system environment variable, and then restarts pycharm, and the problem is found to be perfectly solved.

sys module has many functions, here we introduce some more practical functions, I believe you will like it, and I will walk into the python module!

sys module list of common functions

• sys.argv: implements passing parameters from outside the program to the program.

• sys. Exit ([arg]) : in the middle of the program exit, arg = 0 as normal exit.

• sys.getdefaultencoding(): gets the current code of the system, which is generally ASCII by default.

sys.setdefaultencoding(): set the default code of the system. This method will not be seen when dir (sys) is executed. It cannot be executed in the interpreter. (see set the system default encoding)

• sys. Getfilesystemencoding () : access to the file system using encoding, return the 'MBCS' Windows, MAC returns' utf-8.

• sys. Path : Gets a collection of strings that specify the module search path. You can place the written module in one of the resulting paths and find it correctly when importing in your program.

• sys. Platform : access to current system platform.

• sys. Stdin, sys. Stdout, sys. Stderr : stdin, stdout, and stderr variable contains corresponding with the standard I/O flow stream objects. If you need more control over the output, and print doesn't give you what you want, that's all you need. You can also replace them by redirecting output and input to other devices, or by processing them in a non-standard way

#!/usr/bin/env python

import sys
print sys.argv[0]
print sys.argv[1]

# python sys.py argv1
sys.py
argv1

#!/usr/bin/env python

import sys

def exitfunc(value):
    print value
    sys.exit(0)

print "hello"

try:
    sys.exit(1)
except SystemExit,value:
    exitfunc(value)

print "come?"

# python exit.py
hello
1

>>> import sys
>>> sys.path
['', '/usr/lib/python2.7', '/usr/lib/python2.7/plat-x86_64-linux-gnu', '/usr/lib/python2.7/lib-tk', '/usr/lib/python2.7/lib-old', '/usr/lib/python2.7/lib-dynload', '/usr/local/lib/python2.7/dist-packages', '/usr/lib/python2.7/dist-packages', '/usr/lib/python2.7/dist-packages/PILcompat', '/usr/lib/python2.7/dist-packages/gtk-2.0', '/usr/lib/python2.7/dist-packages/ubuntu-sso-client']

#!/usr/bin/env python

import sys

print sys.modules.keys()

print sys.modules.values()

print sys.modules["os"]

python modules.py
['copy_reg', 'sre_compile', '_sre', 'encodings', 'site', '__builtin__',......

introduction to sys module in Python and usage of package import

1. Argv: implementation from the outside of the program to the program to pass the parameter
in F:\Pywork temp.py file to write the following code :

import sys
print (sys.argv[0])#文件名
print (sys.argv[1])#传入的外部参数
命令行:
F:\Pywork> python temp.py "andy"
temp.py
andy

2. sys. Modules. Keys () returns all have imported module list
3. sys. Exit (n)

sys.path.append("自定义模块路径")

import sys 
sys.stdout.write('HelloWorld!')
print ('Please enter yourname:')
name=sys.stdin.readline()[:-1]
print 'Hi, %s!' % name

import sys 
print("-----------python modules-----------")
print("命令行参数：")
for x in sys.argv:  #sys.argv传递给Python脚本的命令行参数列表。argv[0]是脚本名
    #argv[1]就是执行脚本命令行外部传递的第一个参数，[2]就是第二个
    print(x)
print("Python的路径是：",sys.path)

from sys import argv,path
print("-----------python modules-----------")
print("命令行参数：")
for x in argv:  
    print(x)
print("Python的路径是：",path)

import sys as s
print("-----------python modules-----------")
print("命令行参数：")
for x in s.argv:  
    print(x)
print("Python的路径是：",s.path)

time module is an important function related to timestamp and time

• time.time() generates the current timestamp in the form of a 10-bit integer floating point number. Strftime () generates a time formatted string based on the time tuple. Strptime () generates time tuples based on time formatting strings. time.strptime() and time.strftime() are interoperable.
• time.localtime() generates the time tuple for the current time zone based on the timestamp.
• time.mktime() generates timestamps based on time tuples.

example
A simple example of a timestamp and formatted string is

import time

#生成当前时间的时间戳，只有一个参数即时间戳的位数，默认为10位，输入位数即生成相应位数的时间戳，比如可以生成常用的13位时间戳
def now_to_timestamp(digits = 10):
    time_stamp = time.time()
    digits = 10 ** (digits -10)
    time_stamp = int(round(time_stamp*digits))
    return time_stamp

#将时间戳规范为10位时间戳
def timestamp_to_timestamp10(time_stamp):
    time_stamp = int (time_stamp* (10 ** (10-len(str(time_stamp)))))
    return time_stamp

#将当前时间转换为时间字符串，默认为2017-10-01 13:37:04格式
def now_to_date(format_string="%Y-%m-%d %H:%M:%S"):
    time_stamp = int(time.time())
    time_array = time.localtime(time_stamp)
    str_date = time.strftime(format_string, time_array)
    return str_date

#将10位时间戳转换为时间字符串，默认为2017-10-01 13:37:04格式
def timestamp_to_date(time_stamp, format_string="%Y-%m-%d %H:%M:%S"):
    time_array = time.localtime(time_stamp)
    str_date = time.strftime(format_string, time_array)
    return str_date

#将时间字符串转换为10位时间戳，时间字符串默认为2017-10-01 13:37:04格式
def date_to_timestamp(date, format_string="%Y-%m-%d %H:%M:%S"):
    time_array = time.strptime(date, format_string)
    time_stamp = int(time.mktime(time_array))
    return time_stamp

#不同时间格式字符串的转换
def date_style_transfomation(date, format_string1="%Y-%m-%d %H:%M:%S",format_string2="%Y-%m-%d %H-%M-%S"):
    time_array  = time.strptime(date, format_string1)
    str_date = time.strftime(format_string2, time_array)
    return str_date

test

print(now_to_date())
print(timestamp_to_date(1506816572))
print(date_to_timestamp('2017-10-01 08:09:32'))
print(timestamp_to_timestamp10(1506816572546))
print(date_style_transfomation('2017-10-01 08:09:32'))

is

1506836224000
2017-10-01 13:37:04
2017-10-01 08:09:32
1506816572
1506816572
2017-10-01 08-09-32