Add Python doctest to linear search (#195)

* Add Python doctest to linear search

* Fix conflict

* Rename linear-search.py to linear_search.py

algorithms/Python/searching/linear_search.py

@@ -1,12 +1,17 @@
-def linear_search(a, x):
-    for i in range(len(a)):
-        if a[i] == x:
+arr = [1, 4, 7, 9, 14, 17, 39, 56]
+targets = (8, 39)
+
+
+def linear_search(arr, target):
+    """
+    >>> all(linear_search(arr, x) == arr.index(x) if x in arr else -1 for x in targets)
+    True
+    """
+    for i, item in enumerate(arr):
+        if item == target:
             return i
     return -1
-    
-a = [1,4,7,9,14,17,39,56]    
-x = 8
-y = 39
 
-print(linear_search(a,x))
-print(linear_search(a,y))
+
+for target in targets:
+    print(f"linear_search({arr}, {target}) = {linear_search(arr, target)}")