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# parseActions.py
#
# A sample program a parser to match a date string of the form "YYYY/MM/DD",
# and return it as a datetime, or raise an exception if not a valid date.
#
# Copyright 2012, Paul T. McGuire
#
from datetime import datetime
import pyparsing as pp
from pyparsing import pyparsing_common as ppc
# define an integer string, and a parse action to convert it
# to an integer at parse time
integer = pp.Word(pp.nums).set_name("integer")
def convert_to_int(tokens):
# no need to test for validity - we can't get here
# unless tokens[0] contains all numeric digits
return int(tokens[0])
integer.set_parse_action(convert_to_int)
# or can be written as one line as
# integer = Word(nums).set_parse_action(lambda t: int(t[0]))
# define a pattern for a year/month/day date
date_expr = integer("year") + "/" + integer("month") + "/" + integer("day")
date_expr.ignore(pp.python_style_comment)
def convert_to_datetime(s, loc, tokens):
try:
# note that the year, month, and day fields were already
# converted to ints from strings by the parse action defined
# on the integer expression above
return datetime(tokens.year, tokens.month, tokens.day).date()
except Exception as ve:
errmsg = "'%s/%s/%s' is not a valid date, %s" % (
tokens.year,
tokens.month,
tokens.day,
ve,
)
raise pp.ParseException(s, loc, errmsg)
date_expr.set_parse_action(convert_to_datetime)
date_expr.run_tests(
"""\
2000/1/1
# invalid month
2000/13/1
# 1900 was not a leap year
1900/2/29
# but 2000 was
2000/2/29
"""
)
# if dates conform to ISO8601, use definitions in pyparsing_common
date_expr = ppc.iso8601_date.set_parse_action(ppc.convert_to_date())
date_expr.ignore(pp.python_style_comment)
date_expr.run_tests(
"""\
2000-01-01
# invalid month
2000-13-01
# 1900 was not a leap year
1900-02-29
# but 2000 was
2000-02-29
"""
)
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