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# rangeCheck.py
#
# A sample program showing how parse actions can convert parsed
# strings into a data type or object, and to validate the parsed value.
#
# Copyright 2011, Paul T. McGuire
#
from pyparsing import Word, nums, Suppress, ParseException, empty, Optional
from datetime import datetime
def rangeCheck(minval=None, maxval=None):
# have to specify at least one range boundary
if minval is None and maxval is None:
raise ValueError("minval or maxval must be specified")
# set range testing function and error message depending on
# whether either or both min and max values are given
inRangeFn = {
(True, False) : lambda x : x <= maxval,
(False, True) : lambda x : minval <= x,
(False, False) : lambda x : minval <= x <= maxval,
}[minval is None, maxval is None]
outOfRangeMessage = {
(True, False) : "value %%s is greater than %s" % maxval,
(False, True) : "value %%s is less than %s" % minval,
(False, False) : "value %%s is not in the range (%s to %s)" % (minval,maxval),
}[minval is None, maxval is None]
# define the actual range checking parse action
def rangeCheckParseAction(string, loc, tokens):
parsedval = tokens[0]
if not inRangeFn(parsedval):
raise ParseException(string, loc, outOfRangeMessage % parsedval)
return rangeCheckParseAction
# define the expressions for a date of the form YYYY/MM/DD or YYYY/MM (assumes YYYY/MM/01)
integer = Word(nums).setName("integer")
integer.setParseAction(lambda t:int(t[0]))
month = integer.copy().addParseAction(rangeCheck(1,12))
day = integer.copy().addParseAction(rangeCheck(1,31))
year = integer.copy().addParseAction(rangeCheck(2000, None))
SLASH = Suppress('/')
dateExpr = year("year") + SLASH + month("month") + Optional(SLASH + day("day"))
dateExpr.setName("date")
# convert date fields to datetime (also validates dates as truly valid dates)
dateExpr.setParseAction(lambda t: datetime(t.year, t.month, t.day or 1).date())
# add range checking on dates
mindate = datetime(2002,1,1).date()
maxdate = datetime.now().date()
dateExpr.addParseAction(rangeCheck(mindate, maxdate))
tests = """
2011/5/8
2001/1/1
2004/2/29
2004/2/30
2004/2
""".splitlines()
for t in tests:
t = t.strip()
if not t: continue
print(t)
try:
print(dateExpr.parseString(t)[0])
except Exception as e:
print(str(e))
print()
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