定义

与语言无关，平台无关的可扩展机制，用于序列化结构化数据。类似Json或者XML的数据传输格式和规范，用于不同应用或进程之间进行通信时使用。通信时所传递的信息是通过Protobuf定义的message数据结构进行打包，然后编译成二进制的码流再进行传输或者存储。

优点

我们常用就是xml和json文件。相比这个而言，简单、小、快、兼容性高！。

用法

通过在.proto文件中定义协议缓冲区消息类型来指定您希望如何构建序列化信息。每个协议缓冲区消息都是一个小的逻辑信息记录，包含一系列名称 - 值对。
.proto的用法优点类似c++ 和java。

https://developers.google.com/protocol-buffers/docs/pythontutorial

上面链接是python的demo。
这个写入数据

#! /usr/bin/python
import addressbook_pb2
import sys
# This function fills in a Person message based on user input.
def PromptForAddress(person):
  person.id = int(raw_input("Enter person ID number: "))
  person.name = raw_input("Enter name: ")
  email = raw_input("Enter email address (blank for none): ")
  if email != "":
    person.email = email
  while True:
    number = raw_input("Enter a phone number (or leave blank to finish): ")
    if number == "":
      break
    phone_number = person.phones.add()
    phone_number.number = number
    type = raw_input("Is this a mobile, home, or work phone? ")
    if type == "mobile":
      phone_number.type = addressbook_pb2.Person.MOBILE
    elif type == "home":
      phone_number.type = addressbook_pb2.Person.HOME
    elif type == "work":
      phone_number.type = addressbook_pb2.Person.WORK
    else:
      print "Unknown phone type; leaving as default value."
# Main procedure: Reads the entire address book from a file,
# adds one person based on user input, then writes it back out to the same
# file.
if len(sys.argv) != 2:
  print "Usage:", sys.argv[0], "ADDRESS_BOOK_FILE"
  sys.exit(-1)
address_book = addressbook_pb2.AddressBook()
# Read the existing address book.
try:
  f = open(sys.argv[1], "rb")
  address_book.ParseFromString(f.read())
  f.close()
except IOError:
  print sys.argv[1] + ": Could not open file. Creating a new one."
# Add an address.
PromptForAddress(address_book.people.add())
# Write the new address book back to disk.
f = open(sys.argv[1], "wb")
f.write(address_book.SerializeToString())
f.close()

读取数据

#! /usr/bin/python
import addressbook_pb2
import sys
# Iterates though all people in the AddressBook and prints info about them.
def ListPeople(address_book):
  for person in address_book.people:
    print "Person ID:", person.id
    print " Name:", person.name
    if person.HasField('email'):
      print " E-mail address:", person.email
    for phone_number in person.phones:
      if phone_number.type == addressbook_pb2.Person.MOBILE:
        print " Mobile phone #: ",
      elif phone_number.type == addressbook_pb2.Person.HOME:
        print " Home phone #: ",
      elif phone_number.type == addressbook_pb2.Person.WORK:
        print " Work phone #: ",
      print phone_number.number
# Main procedure: Reads the entire address book from a file and prints all
# the information inside.
if len(sys.argv) != 2:
  print "Usage:", sys.argv[0], "ADDRESS_BOOK_FILE"
  sys.exit(-1)
address_book = addressbook_pb2.AddressBook()
# Read the existing address book.
f = open(sys.argv[1], "rb")
address_book.ParseFromString(f.read())
f.close()
ListPeople(address_book)