Add Access Variables Outside Loop Scope as a Python TIL

python/access-variables-outside-loop-scope.md

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+# Access Variables Outside Loop Scope
+
+Here is a function that loops over a list to find the first occurrence of a
+falsy value.
+
+```python
+def find_false(self):
+    for item in self.items:
+        item_type = type(item)
+        print(f"Current item: {item} ({item_type})")
+        if not item:
+            break
+
+    print(f"First false item: {item} ({item_type})")
+```
+
+Notice how at the end of the function, outside of the loop, I am able to access
+both `item` (defined in the loop definition) and `item_type` (defined within the
+loop's body).
+
+Both of these variables are defined, by the loop, in _function scope_ and are
+accessible anywhere in the function after they have been defined.
+
+The title of this TIL is a bit of a misnomer because Python doesn't have the
+concept of a _loop scope_. There are two levels of scope in Python --
+module/global scope and function scope.
+
+I spend most of my time writing Ruby which also has _block scope_, so Python's
+simplified two-level scoping took me by surprise.
+
+Though the code sample above is contrived, this function scope assignment can be
+taken advantage of with loop definitions in scenarios where you want to know
+what the last `item` defined was before the loop terminated.
+
+```python
+for submission in submissions:
+    if passes(submission, criteria):
+        break
+else:
+    raise ValueError("No submissions that meet given criteria")
+
+print(f"Submit first passing submission: {submission.id}")
+submit(submission)
+```