From 4bf3bb1bb1e2d6d0ccf384ba7110978178cdfaf5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marek=20Ne=C4=8Dada?= <marek@necada.org>
Date: Sun, 3 May 2020 21:29:10 +0300
Subject: [PATCH] "slice" argument type in argproc.py

Former-commit-id: 35117c0a6c09063c41350bb6bc2e07ef2adf97c0
---
 qpms/argproc.py | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)

diff --git a/qpms/argproc.py b/qpms/argproc.py
index bfd1fbf..21d445c 100644
--- a/qpms/argproc.py
+++ b/qpms/argproc.py
@@ -100,6 +100,52 @@ def float_range(string):
         else:
             return np.arange(first, last, increment)
 
+def int_or_None(string):
+    """Tries to parse a string either as an int or None (if it contains only whitespaces)"""
+    try:
+        return int(string)
+    except ValueError as ve:
+        if string.strip() == '':
+            return None
+        else:
+            raise ve
+
+def sslice(string):
+    """Tries to parse a string either as one individual int value
+    or one of the following patterns:
+    
+    first:last:increment
+    first:last
+
+    first, last and increment must be parseable as ints
+    or be empty (then 
+
+    In each case, 's' letter can be prepended to the whole string to avoid
+    argparse interpreting this as a new option (if the argument contains
+    '-' or '+').
+    
+    Returns either int or slice containing ints or Nones.
+    """
+    if string[0] == 's':
+        string = string[1:]
+    try:
+        res = int(string)
+        return res
+    except ValueError:
+        import re
+        match = re.match(r'([^:]*):([^:]*):(.*)', string)
+        if match:
+            step = int_or_None(match.group(3))
+        else:
+            match = re.match(r'([^:]*):(.*)', string)
+            if match:
+                step = None
+            else: 
+                argparse.ArgumentTypeError('Invalid int/slice format: "%s"' % string)
+        start = int_or_None(match.group(1))
+        stop = int_or_None(match.group(2))
+        return slice(start, stop, step)
+
 def sfloat(string):
     '''Tries to match a float, or a float with prepended 's'