Python list

a.Method for creating a list

     1.create list
     eg.
        >>> a=["python",25,89.9]
        >>> a
        ["python",25,89.9]
     2.list index   
     eg.
        >>> a=["python",25,89.9]
        >>> a[0]
        'python'
        >>> a[1]
        25
        >>> a[2]
        89.9
        >>> a[-1]
        89.9
        #get the index ...

Between the characters and numbers in Python is how to compare the size?

1. any two objects can be compared

2. The same type of objects (instances), if it is digital type (int/float/long/complex), in accordance with the simple size to compare; if is non numeric type and class (type) definition of the ...

1.Method for creating a set

 1)s={1,"python"}
 2)s=set("python") or s=set([1,"python"])
   ps. set to list: 
                   lst=list(s)
       list to set(can remove duplicate elements from the set):
                   s=set([1,"python"])  
       Create an immutable set in "frozenset"

2.Common method of set

 1)add 
    eg.
    b ...

Python itself has no switch statement, there are 3 kinds of Solutions:

1.use dictionary

cases = {
           case1: do_some_stuff1,
           case2: do_some_stuff2,
           ...
           caseN: do_some_stuffN,
         }
cases.get(var, do_default_stuff)()

2.use lambda

result = {
  'a': lambda x: x * 5,
  'b': lambda x: x + 7,
  'c': lambda x: x - 2
}[value](x)

3.Beck Brian provides a class switch to ...

Python pickle

import pickle

#dumps(object) :Object serialization
lista=["john","levi","kate"]
listb=pickle.dumps(lista)
#print listb

#loads(string) :The object is restored, and the object type is restored to the original format.
listc=pickle.loads(listb)
#print listc

#dump(object,file) :To store objects in a file.
group1=("cat","is","kkkk")
f1=file ...

python basic grammar

1.Constant and Variable

   1)Ｃonstant
    eg.
      import const
      const.value=5
      print const.value
      const.value=6
   2)Variable
     eg.
        a=1

2.Number and string

   1)Single quotation mark
     eg. a='string'
   2)Double quotation marks
     eg. b="string"
   3)Three single quotation marks (output special characters)
     eg. c='''string ...

Python read and write file

1.Python read and write file

fr=open("readfile.txt","r")  
fw=open("writefile.txt","w")

print fr.readline()  
print fr.tell()

print fr.readlines()  
fw.write("===write line===")  
fw.close()

fr.seek(0,0) #The first parameter represents the number of bytes, after which a parameter represents the relative ...

1.Enable a service to start automatically

1) chkconfig --level 3 SERVICENAME on (old command)    
2) systemctl enable SERVICENAME.service (new command)

2.Disable a service to start automatically

1) chkconfig --level 3 SERVICENAME off (old command)    
2) systemctl disable SERVICENAME.service (new command)

3.View service status(old command and old command)

1) service ...

The operation is very simple, on the 5 step, as follows:

1.login mysql ：

>mysql -uroot -p;

2.Using mysql database：

>use mysql;

3.View user table ：

>SELECT Host,User FROM user;
+--------------+------+-------------------------------------------+
| host         | user | password                                  |
+--------------+------+-------------------------------------------+
| localhost    | root | *A731AEBFB621E354CD41BAF207D884A609E81F5E |
| 192.168.1.1  | root | *A731AEBFB621E354CD41BAF207D884A609E81F5E |
+--------------+------+-------------------------------------------+

4.Update user table ：

>UPDATE user SET Host = '%' WHERE User = 'root ...

RPM(RedHat Package Manager)

Binary package (Binary) as well as the source code package (Source) two. The binary package can be installed directly on the computer, and the source code package will be compiled and installed automatically by the RPM. Source code packages often use src.rpm as a suffix.

1.Common command combination：

-ivh ...