Python Basics: Dictionaries – Access, Iterate, Merge, and Set Operations

Dictionary Operations

The article demonstrates basic dictionary handling in Python. It creates a dictionary

dict1 = {'name':'中国医生','author':'张三','person':'李四','address':'china'}

and shows how to obtain its length with len(dict1), retrieve all keys, values, and items, and prints the results.

dict1 = {'name':'中国医生','author':'张三','person':'李四','address':'china'}
print(len(dict1))
print(dict1.keys())
print(dict1.values())
print(dict1.items())

Four iteration methods are illustrated:

# 1. Iterate over keys
for i in dict1:
    print(i)
# 2. Enumerate keys
for k, v in enumerate(dict1):
    print(k, v)
# 3. Iterate over key‑value pairs
for k, v in dict1.items():
    print(k, v)
# 4. Iterate over values
for v in dict1.values():
    print(v)

Dictionary merging is shown using update. Two dictionaries are defined: dict2 = {"name":"成龙","sex":"男","age":61} and dict3 = {'address':'香港'}. After dict2.update(dict3), the combined dictionary is printed.

dict2 = {"name":"成龙","sex":"男","age":61}
dict3 = {'address':'香港'}
dict2.update(dict3)
print(dict2)

Set Operations

The article then introduces Python sets, emphasizing that they are unordered collections without duplicate elements. A set is created with mixed types:

set1 = {12,34,5,67,True}
print(set1)
print(type(set1))

Common set methods are demonstrated:

Getting the length with len(set1).

Adding elements one at a time using set1.add(98) and set1.add(57).

Adding multiple elements with set1.update([76,2,3]).

print(len(set1))
set1.add(98)
set1.add(57)
print(set1)
set1.update([76,2,3])
print(set1)

Removal operations are covered using a second set set2 = {23,45,67,8,90,87}: set2.pop() removes an arbitrary element. set2.remove(45) deletes a specific element (raises an error if absent). set2.discard(8) safely deletes an element without error. set2.clear() empties the set.

set2 = {23,45,67,8,90,87}
set2.pop()
print(set2)
set2.remove(45)
set2.discard(8)
set2.clear()
print(set2)

Finally, the article shows how to iterate over a set:

for i in set2:
    print(i)

Each code block is followed by the corresponding output shown in the original article, confirming the behavior of the demonstrated operations.