Merge pull request #29 from benfitzpatrick/strftime_strptime

Implement subset of strftime/strptime POSIX standard

isodatetime/data.py

@@ -1313,18 +1313,29 @@ def _tick_over_day_of_month(self):
                                 self.day_of_month = day
                                 return
 
-    def __str__(self, override_custom_dump_format=False):
+    def __str__(self, override_custom_dump_format=False,
+                strftime_format=None):
         if self.expanded_year_digits not in TIMEPOINT_DUMPER_MAP:
             TIMEPOINT_DUMPER_MAP[self.expanded_year_digits] = (
                 dumpers.TimePointDumper(
                     self.expanded_year_digits))
         dumper = TIMEPOINT_DUMPER_MAP[self.expanded_year_digits]
+        if strftime_format is not None:
+            return dumper.strftime(self, strftime_format)
         if self.truncated:
             return dumper.dump(self, self._get_truncated_dump_format())
         if self.dump_format and not override_custom_dump_format:
             return dumper.dump(self, self.dump_format)
         return dumper.dump(self, self._get_dump_format())
 
+    def strftime(self, strftime_format):
+        """Implement equivalent of Python 2's datetime.datetime.strftime.
+
+        Dump based on the format given in the strftime_format string.
+
+        """
+        return self.__str__(strftime_format=strftime_format)
+
     def _get_dump_format(self):
         year_digits = 4 + self.expanded_year_digits
         year_string = "%0" + str(year_digits) + "d"

isodatetime/dumpers.py

@@ -81,6 +81,32 @@ def dump(self, timepoint, formatting_string):
         """
         expression, properties = self._get_expression_and_properties(
             formatting_string)
+        return self._dump_expression_with_properties(
+            timepoint, expression, properties)
+
+    def strftime(self, timepoint, formatting_string):
+        """Implement equivalent of Python 2's datetime.datetime.strftime.
+
+        Dump timepoint based on the format given in formatting_string.
+
+        """
+        split_format = parser_spec.REC_SPLIT_STRFTIME_DIRECTIVE.split(
+            formatting_string)
+        expression = ""
+        properties = []
+        for item in split_format:
+            if parser_spec.REC_STRFTIME_DIRECTIVE_TOKEN.search(item):
+                item_expression, item_properties = (
+                    parser_spec.translate_strftime_token(item))
+                expression += item_expression
+                properties += item_properties
+            else:
+                expression += item
+        return self._dump_expression_with_properties(
+            timepoint, expression, properties)
+
+    def _dump_expression_with_properties(self, timepoint, expression,
+                                         properties):
         if (not timepoint.truncated and
                 ("week_of_year" in properties or
                  "day_of_week" in properties) and

isodatetime/parser_spec.py

@@ -18,6 +18,9 @@
 
 """This provides data to drive ISO 8601 parsing functionality."""
 
+import re
+from . import timezone
+
 
 DATE_EXPRESSIONS = {
     "basic": {
@@ -211,6 +214,47 @@
      "Z", None)
 ]
 
+LOCALE_TIMEZONE_BASIC = timezone.get_timezone_format_for_locale()
+LOCALE_TIMEZONE_BASIC_NO_Z = LOCALE_TIMEZONE_BASIC
+if LOCALE_TIMEZONE_BASIC_NO_Z == "Z":
+    LOCALE_TIMEZONE_BASIC_NO_Z = "+0000"
+LOCALE_TIMEZONE_EXTENDED = timezone.get_timezone_format_for_locale(
+    extended_mode=True)
+LOCALE_TIMEZONE_EXTENDED_NO_Z = LOCALE_TIMEZONE_EXTENDED
+if LOCALE_TIMEZONE_EXTENDED_NO_Z == "Z":
+    LOCALE_TIMEZONE_EXTENDED_NO_Z = "+0000"
+
+# Note: we only accept the following subset of strftime syntax.
+# This is due to inconsistencies with the ISO 8601 representations.
+REC_SPLIT_STRFTIME_DIRECTIVE = re.compile(r"(%\w)")
+REC_STRFTIME_DIRECTIVE_TOKEN = re.compile(r"^%\w$")
+STRFTIME_TRANSLATE_INFO = {
+    "%d": ["day_of_month"],
+    "%H": ["hour_of_day"],
+    "%j": ["day_of_year"],
+    "%m": ["month_of_year"],
+    "%M": ["minute_of_hour"],
+    "%S": ["second_of_minute"],
+    "%X": ["hour_of_day", ":", "minute_of_hour", ":", "second_of_minute"],
+    "%y": ["year_of_century"],
+    "%Y": ["century", "year_of_century"],
+    "%z": LOCALE_TIMEZONE_BASIC_NO_Z,
+}
+STRPTIME_EXCLUSIVE_GROUP_INFO = {
+    "%Y": ("%y",),
+    "%X": ("%H", "%M", "%S")
+}
+
+
+class StrftimeSyntaxError(ValueError):
+
+    """An error denoting invalid or unsupported strftime/strptime syntax."""
+
+    BAD_STRFTIME_INPUT = "Invalid strftime/strptime representation: {0}"
+
+    def __str__(self):
+        return self.BAD_STRFTIME_INPUT.format(*self.args)
+
 
 def get_date_translate_info(num_expanded_year_digits=2):
     expanded_year_digit_regex = "\d" * num_expanded_year_digits
@@ -229,3 +273,50 @@ def get_time_translate_info():
 def get_timezone_translate_info():
     return _TIMEZONE_TRANSLATE_INFO
 
+
+def translate_strftime_token(strftime_token, num_expanded_year_digits=2):
+    """Convert a strftime format into our own dump format."""
+    return _translate_strftime_token(
+        strftime_token, dump_mode=True,
+        num_expanded_year_digits=num_expanded_year_digits
+    )
+
+
+def translate_strptime_token(strptime_token, num_expanded_year_digits=2):
+    """Convert a strptime format into our own parsing format."""
+    return _translate_strftime_token(
+        strptime_token, dump_mode=False,
+        num_expanded_year_digits=num_expanded_year_digits
+    )
+
+
+def _translate_strftime_token(strftime_token, dump_mode=False,
+                              num_expanded_year_digits=2):
+    if strftime_token not in STRFTIME_TRANSLATE_INFO:
+        raise StrftimeSyntaxError(strftime_token)
+    our_translation = ""
+    our_translate_info = (
+        get_date_translate_info(
+            num_expanded_year_digits=num_expanded_year_digits) +
+        get_time_translate_info() +
+        get_timezone_translate_info()
+    )
+    attr_names = STRFTIME_TRANSLATE_INFO[strftime_token]
+    if isinstance(attr_names, basestring):
+        if dump_mode:
+            return attr_names, []
+        return re.escape(attr_names), []
+    attr_names = list(attr_names)
+    for attr_name in list(attr_names):
+        for expr_regex, substitute, format_, name in our_translate_info:
+            if name == attr_name:
+                if dump_mode:
+                    our_translation += format_
+                else:
+                    our_translation += substitute
+                break
+        else:
+            # Not an attribute name, just a delimiter or something.
+            our_translation += attr_name
+            attr_names.remove(attr_name)
+    return our_translation, attr_names