Add find snippets

snippets/find_index.md

@@ -0,0 +1,17 @@
+---
+title: find_index
+tags: list,beginner
+---
+
+Returns the index of the first element in the provided list that satisfies the provided testing function.
+
+Use list comprehension, `enumerate()` and `next()` to return the index of the first element in `lst` for which `fn` returns `True`.
+
+```py
+def find_index(lst, fn):
+  return next(i for i, x in enumerate(lst) if fn(x))
+```
+
+```py
+find_index([1, 2, 3, 4], lambda n: n % 2 == 1) # 0
+```