Character Frequency
Background
Calculating the frequency of characters in a text is a foundational step in cryptography, data compression (like Huffman coding), and natural language processing.
Task
Write a function char_frequency(s: str) -> dict[str, int] that takes a string and returns a dictionary where keys are the characters from the string and values are their corresponding frequencies (counts).
Specifications
- Input: A string
sof arbitrary length. - Output: A dictionary mapping each character to an integer representing how many times it appears in
s.
Constraints
- Do not use
input()orprint(). - The case of characters matters (e.g., 'A' and 'a' are different).
- Whitespace and punctuation should be counted.
- If the string is empty, return an empty dictionary.
Example
>>> char_frequency("hello")
{'h': 1, 'e': 1, 'l': 2, 'o': 1}
>>> char_frequency("aA")
{'a': 1, 'A': 1}
Instructions
Implement the function in solution.py. A dictionary is ideal for storing character counts.