Protobuf是Google開發的序列化結構數據的一套工具，適合用于數據存儲，以及不同語言不同應用之間進行通信的數據交換格式。目前Google提供了C++，Python，Java，Go等語言的支持。

Protobuf的安裝

在Protobuf的github主頁上，google/protobuf，可以找到不同語言的安裝方法。

定義Protobuf格式

syntax = "proto3";// package 在python中沒用，但是在其他語言的工程中可以避免命名沖突package tutorial;import "google/protobuf/timestamp.proto";// [START messages]// message 是包含多個值的集合，支持bool,int32,float,double,string等message Person { /** =1，=2，是每個值唯一對應的tag* 1-15因為使用少于1 byte，通常用來表示repeated的值* >16的數用來表示其他值*/ 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; } /** 每個值都需要一個標記，有三種類型的標記* required: 必須賦值，否則會出現未初始化的錯誤* optional: 可以賦值，可以為空，賦默認值* repeated: 賦任意個數的值*/ 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]

定義好protobuf的格式之后，就需要編譯，得到讀寫該protobuf的類文件。

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

編譯之后將會生成 addressbook_pb2.py。

Protobuf的使用：寫信息

#! /usr/bin/env python# 根據提示，用戶輸入address信息，然后寫入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 用來序列化message，并返回PB化之后的二進制string值。with open(sys.argv[1], "wb") as f: f.write(address_book.SerializeToString())

調用該python文件， 進行符合protobuf格式的數據輸入，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):

然后將會生成一個 address_book_test 的PB化后的二進制文件，類似

test{test@google.com"

0001112222"

1110003333

Protobuf的使用：讀信息

讀信息，也叫做解析PB化的數據。

#! /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)

輸出結果類似于

Person ID: 123

Name: test

E-mail address: test@google.com

Work phone #: 0001112222

Work phone #: 1110003333

Message常用的方法：IsInitialized(): 檢查所有required的值是否已經賦值

_str_(): 用于debug，返回人類可讀的數據

CopyFrom(other_msg): 根據已知message對新message賦值

Clear(): 將所有元素清空

SerializedToString(): 將message數據進行序列化，返回PB化之后的二進制string

ParseFromString(): 將二進制string，解析PB數據，返回message數據

總結

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