Overview:
- The load() method of Python pickle module reads the pickled byte stream of one or more python objects from a file object. When multiple objects are expected from the byte stream, the load() method should be called multiple times.
- A File object in this context means an instance of a class with implementation for the following methods:
- read(number)
- readline()
- Both the methods should return bytes object.
- Conforming to the above interface makes sure that the pickled binary streams may not be loaded from file sources only. They can also be loaded from any buffer sources like BytesIO or any other custom classes.
Example 1: De-serializing pickled objects using pickle.load method
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# import required python modules import pickle import uuid
# Trivial definition of a car class Car: manufacturer = "" modelName = ""
def __init__(self, manufacturer, modelName): self.manufacturer = manufacturer self.modelName = modelName
def identify(self): print("Manufacturer: %s"%(self.manufacturer)) print("Model Name: %s"%(self.modelName))
# Trivial definition of a ServiceRecord class ServiceRecord: id = -1 milesReading = -1 serviceCount = -1
def __init__(self, id, milesReading, serviceCount): self.id = uuid.uuid4() self.milesReading = milesReading self.serviceCount = serviceCount
def identify(self): print("Service Id: %s"%(self.id)) print("Miles: %s"%(self.milesReading)) print("Service Count: %s"%(self.serviceCount))
# Get car and service instances print("Creating objects")
car = Car("Toyota", "Corolla") s1 = ServiceRecord(1, 5000, 1) s2 = ServiceRecord(2, 15000, 2)
# Print object information car.identify() s1.identify() s2.identify()
# Create a file for storing objects objectRep = open("ServiceInfo.picl", "wb")
print("Pickling...") # Pickle the objects pickle.dump(car, objectRep, protocol=pickle.HIGHEST_PROTOCOL) pickle.dump(s1, objectRep, protocol=pickle.HIGHEST_PROTOCOL) pickle.dump(s2, objectRep, protocol=pickle.HIGHEST_PROTOCOL)
# Close the file objectRep.close() print("Pickling complete") print("-------------------")
# Open the file in read mode objectRep = open("ServiceInfo.picl", "rb")
print("Unpickling...") # Unpickle the objects object1 = pickle.load(objectRep) object1.identify()
object2 = pickle.load(objectRep) object2.identify()
object3 = pickle.load(objectRep) object3.identify() print("Unpickling complete")
objectRep.close()
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Output:
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Creating objects Manufacturer: Toyota Model Name: Corolla Service Id: b6c83c8e-4dd1-4d26-8d46-6e3ac002fa14 Miles: 5000 Service Count: 1 Service Id: 1c5a43b7-4c37-4402-a07c-006d0a133c71 Miles: 15000 Service Count: 2 Pickling... Pickling complete ------------------- Unpickling... Manufacturer: Toyota Model Name: Corolla Service Id: b6c83c8e-4dd1-4d26-8d46-6e3ac002fa14 Miles: 5000 Service Count: 1 Service Id: 1c5a43b7-4c37-4402-a07c-006d0a133c71 Miles: 15000 Service Count: 2 Unpickling complete |