Python Data Persistence 简明教程

>>> import sys
>>> x=sys.stdin.readline()
Welcome to TutorialsPoint
>>> x
'Welcome to TutorialsPoint\n'

>>> x=sys.stdin.read()
Hello
Welcome to TutorialsPoint
>>> x
'Hello\nWelcome to TutorialsPoint\n'

>>> x='Welcome to TutorialsPoint\n'
>>> sys.stdout.write(x)
Welcome to TutorialsPoint
26

f=os.open("test.dat", os.O_WRONLY|os.O_CREAT)

data="Hello World".encode('utf-8')

os.write(f,data)

os.close(f)

f=os.open("test.dat", os.O_RDONLY)
data=os.read(f,20)
print (data.decode('utf-8'))

numbers=[10,20,30,40]
   file=open('numbers.txt','w')
   file.write(str(numbers))
   file.close()

numbers=[10,20,30,40]
   data=bytearray(numbers)
   file.write(data)
   file.close()

file=open('numbers.txt','rb')
   data=file.read()
   print (list(data))

open(filename, flag='c', protocol=None, writeback=False)

import shelve
s=shelve.open("test")
s['name']="Ajay"
s['age']=23
s['marks']=75
s.close()

s=shelve.open('test')
print (s['age']) #this will print 23
   s['age']=25
print (s.get('age')) #this will print 25
s.pop('marks') #this will remove corresponding k-v pair

print (list(s.items()))
[('name', 'Ajay'), ('age', 25), ('marks', 75)]

print (list(s.keys()))
['name', 'age', 'marks']

print (list(s.values()))
['Ajay', 25, 75]

d={'salary':10000, 'designation':'manager'}
s.update(d)
print (list(s.items()))

[('name', 'Ajay'), ('age', 25), ('salary', 10000), ('designation', 'manager')]

>>> dbm.whichdb('mydbm.db')
'dbm.dumb'
>>> import dbm
>>> db=dbm.open('mydbm.db','n')
>>> db['name']=Raj Deshmane'
>>> db['address']='Kirtinagar Pune'
>>> db['PIN']='431101'
>>> db.close()

>>> db=dbm.open('mydbm.db','r')
>>> for k,v in db.items():
   print (k,v)
b'name' : b'Raj Deshmane'
b'address' : b'Kirtinagar Pune'
b'PIN' : b'431101'

import json
   data=['Rakesh',{'marks':(50,60,70)}]
   s=json.dumps(data)
json.loads(s)

<?xml version = "1.0" encoding = "iso-8859-1"?>
<studentlist>
   <student>
      <name>Ratna</name>
      <subject>Physics</subject>
      <marks>85</marks>
   </student>
   <student>
      <name>Kiran</name>
      <subject>Maths</subject>
      <marks>100</marks>
   </student>
   <student>
      <name>Mohit</name>
      <subject>Biology</subject>
      <marks>92</marks>
   </student>
</studentlist>

import xml.etree.ElementTree as xmlobj
root=xmlobj.Element('studentList')

student=xmlobj.Element('student')
   nm=xmlobj.SubElement(student, 'name')
   nm.text='name'
   subject=xmlobj.SubElement(student, 'subject')
   nm.text='Ratna'
   subject.text='Physics'
   marks=xmlobj.SubElement(student, 'marks')
   marks.text='85'

root.append(student)

tree = xmlobj.ElementTree(root)
   file = open('studentlist.xml','wb')
   tree.write(file)
   file.close()

tree = xmlobj.ElementTree(file='studentlist.xml')

root = tree.getroot()
children = root.getchildren()

for child in children:
   student={}
   pairs = child.getchildren()
   for pair in pairs:
      product[pair.tag]=pair.text

proplist = {
   "name" : "Ganesh",
   "designation":"manager",
   "dept":"accts",
   "salary" : {"basic":12000, "da":4000, "hra":800}
}

import plistlib
fileName=open('salary.plist','wb')
plistlib.dump(proplist, fileName)
fileName.close()

fp= open('salary.plist', 'rb')
pl = plistlib.load(fp)
print(pl)

pip install pymysql

import sqlite3
db=sqlite3.connect('test.db')

cur=db.cursor()

import sqlite3
db=sqlite3.connect('test.db')
cur =db.cursor()
cur.execute('''CREATE TABLE student (
StudentID INTEGER PRIMARY KEY AUTOINCREMENT,
name TEXT (20) NOT NULL,
age INTEGER,
marks REAL);''')
print ('table created successfully')
db.close()

import sqlite3
db=sqlite3.connect('test.db')
qry="insert into student (name, age, marks) values('Abbas', 20, 80);"
try:
   cur=db.cursor()
   cur.execute(qry)
   db.commit()
print ("record added successfully")
except:
   print ("error in query")
   db.rollback()
db.close()

import sqlite3
db=sqlite3.connect('test.db')
nm=input('enter name')
a=int(input('enter age'))
m=int(input('enter marks'))
qry="insert into student (name, age, marks) values(?,?,?);"
try:
   cur=db.cursor()
   cur.execute(qry, (nm,a,m))
   db.commit()
   print ("one record added successfully")
except:
   print("error in operation")
   db.rollback()
db.close()

qry="update student set age=23 where name='Anil';"

import sqlite3
db=sqlite3.connect('test.db')
nm=input(‘enter name’)
a=int(input(‘enter age’))
qry="update student set age=? where name=?;"
try:
   cur=db.cursor()
   cur.execute(qry, (a, nm))
   db.commit()
   print("record updated successfully")
except:
   print("error in query")
   db.rollback()
db.close()

import sqlite3
db=sqlite3.connect('test.db')
nm=input(‘enter name’)
qry="DELETE from student where name=?;"
try:
   cur=db.cursor()
   cur.execute(qry, (nm,))
   db.commit()
   print("record deleted successfully")
except:
   print("error in operation")
   db.rollback()
db.close()

c:\mongodb\bin>mongod

x:\mongodb\bin>mongo

pip3 install pymongo

from pymongo import MongoClient
client=MongoClient()

client = MongoClient('localhost', 27017)

db=client.newdb

db.create_collection('students')

from pymongo import MongoClient
client=MongoClient()
db=client.newdb
db.create_collection("students")
student=db['students']
studentlist=[{'studentID':1,'Name':'Juhi','age':20, 'marks'=100},
{'studentID':2,'Name':'dilip','age':20, 'marks'=110},
{'studentID':3,'Name':'jeevan','age':24, 'marks'=145}]
student.insert_many(studentlist)
client.close()

students=db['students']
docs=students.find()
for doc in docs:
   print (doc['Name'], doc['age'], doc['marks'] )

students=db['students']
docs=students.find({'age':{'$gt':21}})
for doc in docs:
   print (doc.get('Name'), doc.get('age'), doc.get('marks'))

from pymongo import MongoClient
client=MongoClient()
db=client.newdb
doc=db.students.find_one({'Name': 'Juhi'})
db['students'].update_one({'Name': 'Juhi'},{"$set":{'marks':150}})
client.close()

pip3 install cassandra-driver

from cassandra.cluster import Cluster
clstr=Cluster()

session=clstr.connect()

from cassandra.cluster import Cluster
clstr=Cluster()
session=clstr.connect()
session.execute(“create keyspace mykeyspace with replication={
   'class': 'SimpleStrategy', 'replication_factor' : 3
};”

from cassandra.cluster import Cluster
clstr=Cluster()
session=clstr.connect('mykeyspace')
qry= '''
create table students (
   studentID int,
   name text,
   age int,
   marks int,
   primary key(studentID)
);'''
session.execute(qry)

from cassandra.cluster import Cluster
clstr=Cluster()
session=clstr.connect('mykeyspace')
session.execute("insert into students (studentID, name, age, marks) values
   (1, 'Juhi',20, 200);"

from cassandra.cluster import Cluster
clstr=Cluster()
session=clstr.connect('mykeyspace')
rows=session.execute("select * from students;")
for row in rows:
print (StudentID: {} Name:{} Age:{} price:{} Marks:{}'
   .format(row[0],row[1], row[2], row[3]))

rows=session.execute("select * from students WHERE age>20 allow filtering;")

pip install zodb

pip install openpyxl

from openpyxl import Workbook
wb=Workbook()
sheet1=wb.active
sheet1.title='StudentList'

sheet1['A1']= 'Student List'

cell1=sheet1.cell(row=1, column=1)
cell1.value='Student List'

wb.save('Student.xlsx')

from openpyxl import Workbook
wb = Workbook()
sheet1 = wb.active
sheet1.title='Student List'
sheet1.cell(column=1, row=1).value='Student List'
studentlist=[('RollNo','Name', 'age', 'marks'),(1,'Juhi',20,100),
   (2,'dilip',20, 110) , (3,'jeevan',24,145)]
for col in range(1,5):
   for row in range(1,5):
      sheet1.cell(column=col, row=1+row).value=studentlist[row-1][col-1]
wb.save('students.xlsx')

from openpyxl import load_workbook
wb=load_workbook('students.xlsx')

cell1=sheet1.cell(row=1, column=1)
print (cell1.value)
Student List