About pickle module - 6 points that beginners must know

1.pickle Related soul torture ,who、why？？

(1). who it is?

• pickle Modules can only be Python Use in ,python Almost all data types in （ list , Dictionaries , aggregate , Class etc. ） Both can be used. pickle Serialization
• pickle Serialized data , Poor readability , People generally can't recognize
• Persistent storage , Objects can be stored on disk as files
• You can save the file in any format , But in general pkl,pickle,p、data Equiform . You create your own extension , for example 【.alien】 It's fine too

(2). why is it ?

• When you want to save an object 、 Dictionary time ,ini Format 、xml The format and other configuration files cannot be directly implemented , It needs to be parsed again . but pickle It can be directly parsed
• When you want to save binary files ,pickle It can also come in handy
• Pickle It's portable , Different operating systems , Whether it's mac、windows、linux All can be read pickle file

2.pickle How to use ,how to use ？

(1) Serialize operation object ------- Save to file

Serializing objects ---------------- And write the result data stream to the file object .

with open("test_pickle.pkl", "wb") as f:
    #  serialize , Write object to file 
    pickle.dump(obj, f, protocol=0)



def dump(obj, file, protocol=None):
    Pickler(file, protocol).dump(obj)


class Pickler:

    def __init__(self, file, protocol=None):
        """This takes a file-like object for writing a pickle data stream.

        The optional protocol argument tells the pickler to use the
        given protocol; supported protocols are 0, 1, 2.  The default
        protocol is 0, to be backwards compatible.  (Protocol 0 is the
        only protocol that can be written to a file opened in text
        mode and read back successfully.  When using a protocol higher
        than 0, make sure the file is opened in binary mode, both when
        pickling and unpickling.)

        Protocol 1 is more efficient than protocol 0; protocol 2 is
        more efficient than protocol 1.

• Serialization mode (protocol) Support [0, 1, 2] Three options , The larger the number, the higher the efficiency , It also means that the more severe the compression .
• The default is 0, You can basically see the saved object and list information , But if you choose 1、 or 2, It's basically garbled , It means that the compression ratio is very high
• Follow up screenshots , The effect of different compression ratios

(2) Deserialization operation ------- analysis pickle The file of

Deserialization operation -------------------- The process of parsing data from a file

with open("test_pickle.pkl", "rb") as f:
     obj = pickle.load(f)

3. serialize ---- class (Class) Time code

import pickle


class Person(object):

    def __init__(self, name, age, blog):
        self.name = name
        self.age = age
        self.blog = blog


def do_serializing(file):
    per = Person("alien", 18, "https://blog.csdn.net/chenmozhe22")
    with open(file, "wb") as f:
        pickle.dump(per, f, protocol=0)


def do_unserializing(file):
    with open(file, "rb") as f:
        obj = pickle.load(f)
        print("obj type==========>{}".format(type(obj)))
        print("obj value==========>{},{},{}".format(obj.name, obj.age, obj.blog))


if __name__ == "__main__":
    file_path = r'F:\MyProjects\XXXXX\TestCase\pickle_file.obj'
    do_serializing(file_path)
    do_unserializing(file_path)

#  Print as follows ：

obj type==========><class '__main__.Person'>
obj value==========>alien,18,https://blog.csdn.net/chenmozhe22

4. Serialization mode （protoco） Effects of different values

---

protocol=0 Time compression effect ：

---

protocol=1 Time compression effect ：

5. serialize ---- list (list) Time code

import pickle


def do_serializing(file):
    info_list = ["alien", 18, "https://blog.csdn.net/chenmozhe22"]
    with open(file, "wb") as f:
        pickle.dump(info_list, f, protocol=0)


def do_unserializing(file):
    with open(file, "rb") as f:
        obj = pickle.load(f)
        print("obj type==========>{}".format(type(obj)))
        print("obj value==========>{},{},{}".format(obj[0], obj[1], obj[2]))


if __name__ == "__main__":
    file_path = r'F:\MyProjects\FT_AutoTestDemo\TestCase\pickle_file.pkl'
    do_serializing(file_path)
    do_unserializing(file_path)

#  Print as follows :

obj type==========><type 'list'>
obj value==========>alien,18,https://blog.csdn.net/chenmozhe22

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The serialization effect is as follows ：

6. Decoding problem ---- chinese 、python2&python3 Incompatibility, etc

def do_unserializing(file):
    with open(file, "rb") as f:
        obj = pickle.load(f, encoding='iso-8859-1')					#  Try adding different decodes 

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It's not easy to create , Welcome to one button three link support !!!

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Extended reading ：
《python3 Configuration file ini Use of ---- Reading and writing 、list&dict&path Equivariant ----configparser》
《Python3 How to open a file in （With open）》