Add example of using a type statement

Author: gjbex

source-code/typing/README.md

@@ -24,6 +24,8 @@ Type checking can be done using [mypy](http://mypy-lang.org/index.html).
 1. `dict_incorrect.py`: code that counts the words in a text read from standard
    input.  The counts are subsequently normalized to `float`, which is a type
    error.
+1. `dict_correct_type_statement.py`: same code as `dict_correct.py`, but
+   with a type variable as type statement.
 1. `people_incorrect.py`: code that defines a `People` class, stores some in a
    list with mistakes.
 1. `duck_typing.py`: example code illustrating duck typing.

source-code/typing/dict_correct_type_statement.py

@@ -0,0 +1,26 @@
+#!/usr/bin/env python
+
+import re
+import sys
+
+
+type Count = dict[str, int]
+
+
+def word_count(text: str) -> Count:
+    counts: Count = {}
+    words = re.split(r"\W+", text)
+    for word in words:
+        word = word.lower()
+        if word not in counts:
+            counts[word] = 0
+        counts[word] += 1
+    return counts
+
+
+if __name__ == "__main__":
+    text = " ".join(sys.stdin.readlines())
+    counts = word_count(text)
+    for word, count in counts.items():
+        if word:
+            print(f"{word}: {count}")