add interleave script

interleave.py

@@ -0,0 +1,38 @@
+#!/usr/bin/env python3
+import os
+import sys
+
+from pdfrw import PdfReader, PdfWriter
+
+
+def main(input_files, output_file):
+    cwd = os.getcwd()
+
+    all_pdf_pages = {}
+    lengths = []
+    print(f'loading input files: {input_files}')
+    for pdf_filename in input_files:
+        reader = PdfReader(os.path.join(cwd, pdf_filename))
+        all_pdf_pages[pdf_filename] = reader.pages
+        lengths.append(len(reader.pages))
+
+    assert all([x == lengths[0] for x in lengths])
+
+    interleaved_pdf = PdfWriter()
+    for i in range(lengths[0]):
+        for pdf in all_pdf_pages.values():
+            interleaved_pdf.addpage(pdf[i])
+
+    interleaved_pdf.write(os.path.join(cwd, output_file))
+
+
+def usage():
+    print('Usage: interleave.py output.pdf input1.pdf input2.pdf [input3.pdf ...]')
+
+
+if __name__ == '__main__':
+    if len(sys.argv) < 4:
+        usage()
+        sys.exit(1)
+
+    main(sys.argv[2:], sys.argv[1])