merged changes for lakeshore and ccu4

frappy/lib/units.py

@@ -0,0 +1,50 @@
+# *****************************************************************************
+#
+# This program is free software; you can redistribute it and/or modify it under
+# the terms of the GNU General Public License as published by the Free Software
+# Foundation; either version 2 of the License, or (at your option) any later
+# version.
+#
+# This program is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+# FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+# details.
+#
+# You should have received a copy of the GNU General Public License along with
+# this program; if not, write to the Free Software Foundation, Inc.,
+# 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+#
+# Module authors:
+#   Markus Zolliker <markus.zolliker@psi.ch>
+#
+# *****************************************************************************
+"""handling of prefixes of physical units"""
+
+import re
+import prefixed
+
+prefixed.SI_MAGNITUDE['u'] = 1e-6  # accept 'u' as replacement for 'µ'
+
+
+class NumberWithUnit:
+    def __init__(self, *units):
+        pfx = "|".join(prefixed.SI_MAGNITUDE)
+        unt = "|".join(units)
+        self.units = units
+        self.pattern = re.compile(rf'\s*([+-]?\d*\.?\d*(?:[eE][+-]?\d+)?\s*(?:{pfx})?)({unt})\s*$')
+
+    def parse(self, value):
+        """parse and return number and value"""
+        match = self.pattern.match(value)
+        if not match:
+            raise ValueError(f'{value!r} can not be interpreted as a number with unit {",".join(self.units)}')
+        number, unit = match.groups()
+        return prefixed.Float(number), unit
+
+    def getnum(self, value):
+        """parse and return value only"""
+        return self.parse(value)[0]
+
+
+def format_with_unit(value, unit='', digits=3):
+    return f'{prefixed.Float(value):.{digits}H}{unit}'