More readable in out logic

Author: rhpvorderman

src/isal/igzip.py

@@ -282,32 +282,32 @@ def main():
 
     compresslevel = args.compresslevel or _COMPRESS_LEVEL_TRADEOFF
 
-    if args.file is None:
-        if args.compress:
-            in_file = sys.stdin.buffer
+    if args.compress and args.file is None:
+        in_file = sys.stdin.buffer
+        out_file = IGzipFile(mode="wb", compresslevel=compresslevel,
+                             fileobj=sys.stdout.buffer)
+    elif args.compress and args.file is not None:
+        in_file = io.open(args.file, mode="rb")
+        if args.stdout:
             out_file = IGzipFile(mode="wb", compresslevel=compresslevel,
                                  fileobj=sys.stdout.buffer)
         else:
-            in_file = IGzipFile(mode="rb", fileobj=sys.stdin.buffer)
+            out_file = open(args.file + ".gz", mode="wb",
+                            compresslevel=compresslevel)
+    elif not args.compress and args.file is None:
+        in_file = IGzipFile(mode="rb", fileobj=sys.stdin.buffer)
+        out_file = sys.stdout.buffer
+    elif not args.compress and args.file is not None:
+        if args.stdout:
             out_file = sys.stdout.buffer
-    else:
-        if args.compress:
-            in_file = io.open(args.file, mode="rb")
-            if args.stdout:
-                out_file = IGzipFile(mode="wb", compresslevel=compresslevel,
-                                     fileobj=sys.stdout.buffer)
-            else:
-                out_file = open(args.file + ".gz", mode="wb",
-                                compresslevel=compresslevel)
         else:
             base, extension = os.path.splitext(args.file)
             if extension != ".gz":
-                raise ValueError(f"filename doesn't end in .gz: {args.file}")
-            in_file = open(args.file, "rb")
-            if args.stdout:
-                out_file = sys.stdout.buffer
-            else:
-                out_file = io.open(base, "wb")
+                raise ValueError(f"filename doesn't end in .gz: {args.file}. "
+                                 f"Cannot determine filename for output")
+            out_file = io.open(base, "wb")
+        in_file = open(args.file, "rb")
+
     try:
         while True:
             block = in_file.read(BUFFER_SIZE)