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python-dictionary
Dictionaries are used to store data values in key:value pairs.
A dictionary is a collection which is ordered*, changeable and do not allow duplicates.
*As of Python version 3.7, dictionaries are ordered. In Python 3.6 and earlier, dictionaries are unordered.
Dictionaries are written with curly brackets, and have keys and values:
# Create and print a dictionary:
thisdict = {
"brand": "Ford",
"model": "Mustang",
"year": 1964
}
print(thisdict)Iterating:
Iterate through Value
To iterate through all values of a dictionary in Python using .values(), you can employ a for loop, accessing each value sequentially. This method allows you to process or display each individual value in the dictionary without explicitly referencing the corresponding keys.
Example: In this example, we are using the values() method to print all the values present in the dictionary.
# create a python dictionary
d = {"name": "Geeks", "topic": "dict", "task": "iterate"}
# loop over dict values
for val in d.values():
print(val)Iterate through keys
In Python, just looping through the dictionary provides you its keys. You can also iterate keys of a dictionary using built-in `.keys()` method.
# create a python dictionary
d = {"name": "Geeks", "topic": "dict", "task": "iterate"}
# default loooping gives keys
for keys in d:
print(keys)
# looping through keys
for keys in d.keys():
print(keys)Iterate through both keys and values
You can use the built-in items() method to access both keys and items at the same time. items() method returns the view object that contains the key-value pair as tuples.
# create a python dictionary
d = {"name": "Geeks", "topic": "dict", "task": "iterate"}
# iterating both key and values
for key, value in d.items():
print(f"{key}: {value}")Sorting:
Lambda function accesses the key (item[0]) during sorting. It offers flexibility if you want to tweak the sorting logic later.
import operator
a = {"Gfg": 5, "is": 7, "Best": 2, "for": 9, "geeks": 8}
res = dict(sorted(a.items(), key=lambda item: item[0]))
print(res){'Best': 2, 'Gfg': 5, 'is': 7, 'geeks': 8, 'for': 9}
Explanation: `lambda item: item[0]` sorts the dictionary by the first element of each tuple (the key).