Python list generation application method

Online application of list generation

It is recommended to read firstPython list generation formula and dictionary generation formula, let’s look at this article again.

Optimization method of select statement

In [1]: import MySQLdb as mysql

In [2]: conn=(user='root',host='127.0.0.1',passwd='123456',db='lyz',charset='utf8')

In [3]: (True)

In [4]: cur = ()

In [5]: info = ['id','name','name_cn','email','mobile']

In [6]: sql = 'select %s from users'%','.join(info)

In [7]: sql
Out[7]: 'select id,name,name_cn,email,mobile from users'

In [8]: (sql)
Out[8]: 2L

In [9]: res = ()  # fetchall() obtains a nested tuple
In [10]: res
Out[10]:
((1L,
  u'liuyongzhan',
  u'\u5218\u6c38\u6808',
  u'1665439369@',
  u'2147483647'),
 (6L, u'lyz', u'1111', u'1111', u'1111'))

Advanced usage:

Turn nested tuples into a list with nested dictionaries in the list

In [11]: ha = [dict((k,row[i]) for i,k in enumerate(info)) for row in res]

In [12]: ha
Out[12]:
[{'email': u'1665439369@',
  'id': 1L,
  'mobile': u'2147483647',
  'name': u'liuyongzhan',
  'name_cn': u'\u5218\u6c38\u6808'},
 {'email': u'1111',
  'id': 6L,
  'mobile': u'1111',
  'name': u'lyz',
  'name_cn': u'1111'}]

Optimization method of insert statement

High-level writing method:

data = dict()  # Or the front-end can be directly passed in json format, and it can be written as data=request.get_json()ZiChan = ['hostname','cpu','mem','exdate','author','note']
sql='insert into zichan (%s) values (%s)'%(','.join(ZiChan),','.join(['"%s"'%data[x][0] for x in ZiChan]))

It's also possible:

data = {'name':'lyz','age':26,'mobile':15768216871,'email':'1665439369@'}
key,values = [],[]                                                       
for k,v in ():                                                       
    (k)
    ('"%s"'%v)
sql = 'insert into users (%s) values (%s)'%(','.join(key),','.join(values))
Execution results：
'insert into users (mobile,age,name,email) values ("15768216871","26","lyz","1665439369@")'

How to optimize update statements

General writing:

ida = ('id')
hostname = ('hostname')
cpu = ('cpu')
mem = ('mem')
exdate = ('exdate')
author = ('author')
note = ('note')
sql = 'update zichan set hostname ="%s",cpu ="%s",mem ="%s",exdate ="%s",author ="%s",note ="%s" where id=%s'%(hostname,cpu,mem,exdate,author,note,ida)

High-level writing method:

Method 1:

data = dict()
ida = ('id',None)[0]
ZiChan = ['hostname','cpu','mem','exdate','author','note']
arr = ["%s='%s'" %(k,data[k][0]) for k in ZiChan]
sql = 'update zichan set %s where id=%s'%(','.join(arr),ida)

Method 2: The writing method of method 2 is the best, so if the front-end passes the field, the corresponding field will be updated. The fields will not be written to death.

Method 1 mainly means that the data transmitted from the front-end jquery is not optimized. If the front-end is transmitted in json format, and it contains an id key and a data key, the id will only correspond to one id, and the value of data is a dictionary. In the dictionary, each asset information field is used as the key, the following method can be used:

data = request.get_json()
ida = ('id',None)
data = ('data',None)
arr = ["%s='%s'"%(k,data[k] for k in data)]   # The result is: ["'hostname'='xxx'","'cpu'='xxx'",......]sql = 'update zichan set %s where id=%s'%(','.join(arr),ida)

Summarize

The above is personal experience. I hope you can give you a reference and I hope you can support me more.