diff --git a/code.py b/code.py
deleted file mode 100644
index 7bfc82b..0000000
--- a/code.py
+++ /dev/null
@@ -1,16 +0,0 @@
-def function1(a):
-    b = dict()
-    for c in a:
-        if c not in b:
-            b[c] = 1
-        else:
-            b[c] += 1
-    return b
-
-def function2(a):
-    print('freqs')
-    total = float(sum([a[b] for b in a.keys()]))
-    for b in a.keys():
-        print(b + ':' + str(a[b]/total))
-
-function2(function1('ATCTGACGCGCGCCGC'))
diff --git a/print_proportions.py b/print_proportions.py
new file mode 100644
index 0000000..8fed6ae
--- /dev/null
+++ b/print_proportions.py
@@ -0,0 +1,15 @@
+import collections
+
+def print_proportions(seq):
+    """Print the proportions of each base in the string `seq`."""
+
+    counts = collections.Counter(seq)
+    total = counts.total()
+
+    # It's printing proportions here, not frequencies, but we'll keep this label for
+    # backwards compatibility.
+    print('freqs')
+    for base, n in counts.items():
+        print(f'{base}:{n/total}')
+
+print_proportions('ATCTGACGCGCGCCGC')