Add support for combined datasets and analysis

sanity_check/csvdiff.py

@@ -0,0 +1,44 @@
+#!/usr/bin/env python3
+"""
+csvdiff.py file1.csv file2.csv
+Streams both files; prints the first differing line or
+‘No differences found’. Uses O(1) memory.
+"""
+
+import sys
+from itertools import zip_longest
+from pathlib import Path
+
+def open_checked(p: str):
+    print(p)
+    path = Path(p)
+    try:
+        return path.open("r", newline=""), path
+    except FileNotFoundError:
+        sys.exit(f"Error: {path} not found")
+
+def human(n: int) -> str:
+    return f"{n:,}"
+
+def main(a_path: str, b_path: str) -> None:
+    fa, a = open_checked(a_path)
+    fb, b = open_checked(b_path)
+
+    with fa, fb:
+        for idx, (ra, rb) in enumerate(zip_longest(fa, fb), 1):
+            if ra != rb:
+                print(f"Files differ at line {human(idx)}")
+                if ra is None:
+                    print(f"{a} ended early")
+                elif rb is None:
+                    print(f"{b} ended early")
+                else:
+                    print(f"{a}: {ra.rstrip()}")
+                    print(f"{b}: {rb.rstrip()}")
+                return
+    print("No differences found")
+
+if __name__ == "__main__":
+    if len(sys.argv) != 3:
+        sys.exit("Usage: csvdiff.py file1.csv file2.csv")
+    main(sys.argv[1], sys.argv[2])