pickle.dump() and pickle.load() for file operations

• Serialization: The process of converting an object into a sequence of bytes is called serialization of an object. Object information can be stored permanently

• Deserialization: The process of restoring a sequence of bytes into an object is called object deserialization. Create the last program saved object

Serialization:

pickle.dump(obj, file,protocol)

Note: Save the object obj to the file file.

• file must have the write() interface, file can be a file opened with 'w' or a StringIO object or any other object that implements the write() interface.
• protocol is the protocol version used for serialization,
• 0: ASCII protocol, the serialized object is represented by printable ASCII code;
• 1: old-fashioned binary protocol;
• 2: The new binary protocol introduced in version 2.3 is more efficient than the previous one.
• The default value of protocol is 0.

import pickle

#使用pickle模块将数据对象保存到文件

data1 = {
    
    'a': [1, 2.0, 3, 4+6j],
         'b': ('string', u'Unicode string'),
         'c': None}

selfref_list = [1, 2, 3]
selfref_list.append(selfref_list[:])

output = open('data.txt', 'wb')

# pickle字典使用协议0。
pickle.dump(data1, output)

# 使用可用的最高协议Pickle列表。
pickle.dump(selfref_list, output, -1)

output.close()

Deserialize:

pickle.load(file)

#使用pickle模块从文件中重构python对象
pkl_file = open('data.txt', 'rb')

data1 = pickle.load(pkl_file)

print(data1)

data2 = pickle.load(pkl_file)
print(data2)

pkl_file.close()

{'a': [1, 2.0, 3, (4+6j)], 'b': ('string', 'Unicode string'), 'c': None}
[1, 2, 3, [1, 2, 3]]

When is serialization required?

• When you want to save the in-memory object state to a file or database;
• When you want to use sockets to transfer objects over the network;
• When you want to transfer objects via RMI;
• (The most commonly used may be stored in the database)