Return errors when found or None otherwise

This commit adds a number of functions that return the error object
when an error is found, or `None` otherwise. It avoids the use of
exceptions as control flow constructs.

1 files changed, 8 insertions, 0 deletions

diff --git a/quality_control/errors.py b/quality_control/errors.py
index 29a38f9..1eda646 100644
--- a/quality_control/errors.py
+++ b/quality_control/errors.py
@@ -1,5 +1,7 @@
 """Hold exceptions for QC package"""
 
+from collections import namedtuple
+
 class InvalidCellValue(Exception):
     """Raised when a function encounters an invalid value"""
 
@@ -22,3 +24,9 @@ class ParseError(Exception):
     """Raised if any of the above exceptions are raised"""
     def __init__(self, *args):
         super().__init__(*args)
+
+InvalidValue = namedtuple(
+    "InvalidValue", ("line_number", "column_number", "value", "message"))
+
+DuplicateHeading = namedtuple(
+    "InvalidValue", ("line_number", "heading", "columns","message"))