Protobuf是Google开发的序列化结构数据的一套工具，适合用于数据存储，以及不同语言不同应用之间进行通信的数据交换格式。目前Google提供了C++，Python，Java，Go等语言的支持。

Protobuf的安装

在Protobuf的github主页上，google/protobuf，可以找到不同语言的安装方法。

定义Protobuf格式

syntax = "proto3";// package 在python中没用，但是在其他语言的工程中可以避免命名冲突package tutorial;import "google/protobuf/timestamp.proto";// [START messages]// message 是包含多个值的集合，支持bool,int32,float,double,string等message Person { /** =1，=2，是每个值唯一对应的tag* 1-15因为使用少于1 byte，通常用来表示repeated的值* >16的数用来表示其他值*/ string name = 1; int32 id = 2; // Unique ID number for this person. string email = 3; enum PhoneType { MOBILE = 0; HOME = 1; WORK = 2; } message PhoneNumber { string number = 1; PhoneType type = 2; } /** 每个值都需要一个标记，有三种类型的标记* required: 必须赋值，否则会出现未初始化的错误* optional: 可以赋值，可以为空，赋默认值* repeated: 赋任意个数的值*/ repeated PhoneNumber phones = 4; google.protobuf.Timestamp last_updated = 5;}// Our address book file is just one of these.message AddressBook { repeated Person people = 1;}// [END messages]

定义好protobuf的格式之后，就需要编译，得到读写该protobuf的类文件。

protoc -I=$SRC_DIR --python_out=$DST_DIR $SRC_DIR/addressbook.proto

编译之后将会生成 addressbook_pb2.py。

Protobuf的使用：写信息

#! /usr/bin/env python# 根据提示，用户输入address信息，然后写入AddressBook中。import addressbook_pb2import systry: raw_input # Python 2except NameError: raw_input = input # Python 3# 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: with open(sys.argv[1], "rb") as f: address_book.ParseFromString(f.read())except IOError: print(sys.argv[1] + ": File not found. Creating a new file.")# Add an address.PromptForAddress(address_book.people.add())# Write the new address book back to disk.# SerializeToString 用来序列化message，并返回PB化之后的二进制string值。with open(sys.argv[1], "wb") as f: f.write(address_book.SerializeToString())

调用该python文件， 进行符合protobuf格式的数据输入，例如

$ python add_person.py address_book_test

Enter person ID number: 123

Enter name: test

Enter email address (blank for none): test@google.com

Enter a phone number (or leave blank to finish): 0001112222

Is this a mobile, home, or work phone? work

Enter a phone number (or leave blank to finish): 1110003333

Is this a mobile, home, or work phone? work

Enter a phone number (or leave blank to finish):

然后将会生成一个 address_book_test 的PB化后的二进制文件，类似

test{test@google.com"

0001112222"

1110003333

Protobuf的使用：读信息

读信息，也叫做解析PB化的数据。

#! /usr/bin/env pythonfrom __future__ import print_functionimport addressbook_pb2import 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.email != "": print(" E-mail address:", person.email) for phone_number in person.phones: if phone_number.type == addressbook_pb2.Person.MOBILE: print(" Mobile phone #:", end=" ") elif phone_number.type == addressbook_pb2.Person.HOME: print(" Home phone #:", end=" ") elif phone_number.type == addressbook_pb2.Person.WORK: print(" Work phone #:", end=" ") 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.with open(sys.argv[1], "rb") as f: address_book.ParseFromString(f.read())ListPeople(address_book)

输出结果类似于

Person ID: 123

Name: test

E-mail address: test@google.com

Work phone #: 0001112222

Work phone #: 1110003333

Message常用的方法：IsInitialized(): 检查所有required的值是否已经赋值

_str_(): 用于debug，返回人类可读的数据

CopyFrom(other_msg): 根据已知message对新message赋值

Clear(): 将所有元素清空

SerializedToString(): 将message数据进行序列化，返回PB化之后的二进制string

ParseFromString(): 将二进制string，解析PB数据，返回message数据