python: typehinting post3.10 syntax

Programming_Languages/Python/Concepts/Type_hinting.md

@@ -8,6 +8,8 @@ tags: [python, types]
 
 With type hinting we can add type information to variables, functions, and classes. This is not enforced by the Python interpreter but can be used by external tools like `mypy` to check the code.
 
+Prior to 3.10, to use types you would have to import the types you wanted `from` the `typing` module. With later versions you can use them directly without importing from `typing`.
+
 ## Basic syntax
 
 ### Variables
@@ -30,11 +32,18 @@ def greet(name: str) -> str:
 
 ## Complex data types
 
-// TODO: Give examples of lists, tuples, dictionaries, sets
+We can type complex data types such as dictionaries, lists, tuples etc.
 
-## Custom dictionay types
+The following function takes a tuple comprising two integers as a parameter and returns a list of ints:
 
-We can create custom dictionay types in the manner of TypeScript types and interfaces as follows:
+```py
+def populate_pair_values(pair: tuple[int, int]) -> list[int]:
+    return [i for i in range(pair[0], pair[1] + 1)]
+```
+
+## Custom dictionary types
+
+We can create custom dictionary types in the manner of TypeScript types and interfaces as follows:
 
 ```py
 class ArticleInfo(TypedDict):
@@ -46,7 +55,7 @@ class ArticleInfo(TypedDict):
 We could then use it thus:
 
 ```py
-def parse_articles() -> List[ArticleInfo]:
+def parse_articles() -> list[ArticleInfo]:
 ```
 
 ## Optional types
@@ -56,7 +65,7 @@ def parse_articles() -> List[ArticleInfo]:
 ```py
 from typing import Optional
 
-def find_index(numbers: List[int], target: int) -> Optional[int]:
+def find_index(numbers: list[int], target: int) -> Optional[int]:
     try:
         return numbers.index(target)
     except ValueError:
@@ -65,6 +74,16 @@ def find_index(numbers: List[int], target: int) -> Optional[int]:
 
 The function above returns an `int` or `None`.
 
+Post 3.10, we don't need to use `Optional`, we can use a union to cover the `None` case. Refactoring the previous example:
+
+```py
+def find_index(numbers: list[int], target: int) -> int | None:
+    try:
+        return numbers.index(target)
+    except ValueError:
+        return None
+```
+
 ## Union types
 
 `Union` can be used to indicate that a variable can be one of several types.
@@ -90,3 +109,11 @@ def my_function() -> List[int]:
 def my_function() -> List[Union[int, float]]:
     return [1, 2, 3]
 ```
+
+Post 3.10 we can use `|` syntax instead of importing `Union`. E.g:
+
+```py
+
+def add(a: int | float, b: int | float) -> int | float:
+    return a + b
+```