###### tags: `python`

# pickle

## Pickle定義

**物件序列化：**直接保存物件狀態，在下次重新執行程式時讀取以恢復運算時必要的資料

- 檔案可能會比原本純文字版本更大
- 產生Pickle File的精神是直接物件交換到另一個Python Program，繼續做後續運算，並且載入時間縮短

## 將資料存成pickle格式的檔案

import pickle
# 注意：使用 pickle 的時候，檔名不可以命名成 pickle.py 

a = [1,3,5,7,9]
d = {'cat':1000, 2:['1','a','XX',3], '3':{'k':'tao', 6:10}}
s = 'my name'

# 存資料
with open('my_file.pickle','wb') as file:
    pickle.dump(a, file) # 使用 dump 把 data 倒進去 file 裡面
    pickle.dump(d, file)
    pickle.dump(s, file)

## 讀取pickle格式的檔案

import pickle
# 注意：使用 pickle 的時候，檔名不可以命名成 pickle.py 

# 拿資料
with open('my_file.pickle','rb') as file1:
    print(file1)
    a = pickle.load(file1) # 逐行拿資料，包括可以拿到 data type
    d = pickle.load(file1)
    s = pickle.load(file1)
    print(a)
    print(d)
    print(s)

## 實務範例

import pickle

class DVD:
    def __init__(self, title, year=None, duration=None, director_id=None):
        self.title = title
        self.year = year
        self.duration = duration
        self.director_id = director_id
        self.filename = self.title.replace(' ', '_') + '.pickle'

    def check_filename(self, filename):
        if filename is not None:
            self.filename = filename


    def save(self, filename=None):
        self.check_filename(filename)
        fh = None
        try:
            data = (self.title, self.year, self.duration, self.director_id)
            fh = open(self.filename, 'wb')
            pickle.dump(data, fh)
        except (EnvironmentError, pickle.PicklingError) as err:
            print(str(err))
            raise SaveError(str(err))
        finally:
            if fh is not None:
                fh.close()

    def load(self, filename=None):
        self.check_filename(filename)
        fh = None
        try:
            fh = open(self.filename, 'rb')
            data = pickle.load(fh)
            (self.title, self.year, self.duration, self.director_id) = data
        except (EnvironmentError, pickle.PicklingError) as err:
            raise LoadError(str(err))
        finally:
            if fh is not None:
                fh.close()


# filename = 'PyConTutorial2013.pickle'
# dvd1 = DVD('PyCon Tutorial', 2013, 1, 'Justin Lin')
# dvd1.save()
 
# dvd2 = DVD('PyCon Tutorial')
# dvd2.load()

# attrs = vars(dvd2) # 可以把物件內的屬性變成字典型態

# for title, value in attrs.items():
#     print(title, ': ', value)



filename = 'PyConTutorial2013.pickle'
dvd1 = DVD('[工具] 建置自己的同步備份系統 – Nextcloud', 2018, 1, '一介資男')
dvd1.save()
 
dvd2 = DVD('[工具] 建置自己的同步備份系統 – Nextcloud')
dvd2.load()

attrs = vars(dvd2) # 可以把物件內的屬性變成字典型態

for title, value in attrs.items():
    print(title, ': ', value)

## 使用csv儲存資料(不使用pickle)

import csv

class DVD:
    def __init__(self, title, year=None, duration=None, director_id=None):
        self.title = title
        self.year = year
        self.duration = duration
        self.director_id = director_id
        self.filename = self.title.replace(' ', '_') + '.csv'

    def check_filename(self, filename):
        if filename is not None:
            self.filename = filename


    def save(self, filename=None):
        self.check_filename(filename)
        fh = None
        try:
            data = (self.title, self.year, self.duration, self.director_id)
            fh = open(self.filename, 'w')
            csvWriter = csv.writer(fh)
            csvWriter.writerow(data)
        except Exception as err:
            raise SaveError(str(err))
        finally:
            if fh is not None:
                fh.close()

    def load(self, filename=None):
        self.check_filename(filename)
        fh = None
        try:
            fh = open(self.filename, 'r')
            csvReader = csv.reader(fh)
            csvList = list(csvReader)
            print(csvList)
            (self.title, self.year, self.duration, self.director_id) = csvList[0]
        except Exception as err:
            raise LoadError(str(err))
        finally:
            if fh is not None:
                fh.close()


filename = 'PyConTutorial2013.pickle'
dvd1 = DVD('[工具] 建置自己的同步備份系統 – Nextcloud', 2018, 1, '一介資男')
dvd1.save()
 
dvd2 = DVD('[工具] 建置自己的同步備份系統 – Nextcloud')
dvd2.load()

attrs = vars(dvd2) # 可以把物件內的屬性變成字典型態

for title, value in attrs.items():
    print(title, ': ', value)