Python Dictionary Construction Using A Mapping Object

Overview of dict(mapping):

  • Dictionaries can be created using an existing mapping object.
  • A mapping object is an object that implements the interface as defined by the collections.abc.mapping class.
  • The class dict which implements the dictionary behaviour in Python is derived from the collections.abc.mapping class.
  • In other words, a dictionary can be created from another dictionary. As of now Python has only one mapping type and it is the dict type.

Example:

# Example Python program that creates
# a dictionary instance from an existing mapping
# instance

# A dictionary of pids vs their bytes in physical memory
pidVsMem = {141:14812,
            131:29613,
            129:48349};

# Create a dictionary from an existing dictionary
snapshot = dict(pidVsMem);
print("Snapshot:");
print(snapshot);

# Remove the key-value for the smallest key
snapshotKeys = snapshot.keys();
snapshot.pop(min(snapshotKeys));
print("Snapshot-updated:");
print(snapshot);

Output:

Snapshot:
{141: 14812, 131: 29613, 129: 48349}
Snapshot-updated:
{141: 14812, 131: 29613}

 


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