1 files changed, 34 insertions, 0 deletions
diff --git a/challenge-283/steven-wilson/python/ch-1.py b/challenge-283/steven-wilson/python/ch-1.py
new file mode 100644
index 0000000000..d95b9b5534
--- /dev/null
+++ b/challenge-283/steven-wilson/python/ch-1.py
@@ -0,0 +1,34 @@
+#!/usr/bin/env python3
+
+from collections import Counter
+
+
+def unique_number(integers):
+    """ Given an array of integers, where every element appears more than once
+    except one element, return the one element that appears exactly one time.
+
+    >>> unique_number([3, 3, 1])
+    1
+    >>> unique_number([3, 2, 4, 2, 4])
+    3
+    >>> unique_number([1])
+    1
+    >>> unique_number([4, 3, 1, 1, 1, 4])
+    3
+    """
+    if not all(isinstance(i, int) for i in integers):
+        raise ValueError('The array should only contain integers')
+
+    counter = Counter(integers)
+    unique = [k for k, v in counter.items() if v == 1]
+
+    if len(unique) != 1:
+        raise ValueError('There should be one unique element in the array')
+
+    return unique[0]
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod(verbose=True)