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https://issues.apache.org/jira/browse/BEAM-7018?focusedWorklogId=280426&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-280426
]
ASF GitHub Bot logged work on BEAM-7018:
----------------------------------------
Author: ASF GitHub Bot
Created on: 22/Jul/19 14:15
Start Date: 22/Jul/19 14:15
Worklog Time Spent: 10m
Work Description: robertwb commented on pull request #8859: [BEAM-7018]
Added Regex transform for PythonSDK
URL: https://github.com/apache/beam/pull/8859#discussion_r305867189
##########
File path: sdks/python/apache_beam/transforms/util.py
##########
@@ -864,3 +867,225 @@ def add_window_info(element,
timestamp=DoFn.TimestampParam,
def expand(self, pcoll):
return pcoll | ParDo(self.add_window_info)
+
+
+class Regex(object):
+ """
+ PTransform to use Regular Expression to process the elements in a
+ PCollection.
+ """
+ @staticmethod
+ def _regex_compile(regex):
+ """Return re.compile if the regex has a string value"""
+ if isinstance(regex, str):
+ regex = re.compile(regex)
+ return regex
+
+ @staticmethod
+ @ptransform_fn
+ def _matches_all_object(pcoll, regex, group=None):
+ """
+ PTransform to find the matches as per the regex.
+ """
+ def _process(element):
+ m = regex.finditer(element)
+ results = list()
+ for _, match in enumerate(m, start=1):
+ results.append(match.group())
+ for groupNum in range(0, len(match.groups())):
+ results.append(match.group(groupNum + 1))
+ if results:
+ yield results
+ return pcoll | FlatMap(_process)
+
+ @staticmethod
+ @ptransform_fn
+ def _matches_kv_object(pcoll, regex, keyGroup, valueGroup):
+ """
+ PTransfrom to find the matches as per regex and return as a KV pair.
+ """
+ def _process(element):
+ match = regex.match(element)
+ if match:
+ yield (match.group(keyGroup), match.group(valueGroup))
+
+ return pcoll | FlatMap(_process)
+
+ @staticmethod
+ @typehints.with_input_types(str)
+ @typehints.with_output_types(str)
+ @ptransform_fn
+ def matches(pcoll, regex, group=None):
+ """
+ Returns the matches if the entire line matched the Regex. Returns the
+ entire line (group 0 by default). Group can be integer value and a string
+ value.
+
+ Args:
+ regex: the regular expression string or (re.compile) pattern.
+ group: (optional) name of the group, it can be integer or a string value.
+ """
+ regex = Regex._regex_compile(regex)
+ group = group or 0
+
+ def _process(element):
+ m = regex.match(element)
+ if m:
+ yield m.group(group)
+ return pcoll | FlatMap(_process)
+
+ @staticmethod
+ @typehints.with_input_types(str)
+ @typehints.with_output_types(str)
+ @ptransform_fn
+ def all_matches(pcoll, regex):
+ """
+ Returns the matches if the entire line matches the Regex. Returns all
+ groups.
+
+ Args:
+ regex: the regular expression string or (re.compile) pattern.
+ """
+ regex = Regex._regex_compile(regex)
+ return pcoll | Regex._matches_all_object(regex=regex)
+
+ @staticmethod
+ @typehints.with_input_types(str)
+ @typehints.with_output_types(typehints.KV[K, V])
+ @ptransform_fn
+ def matches_kv(pcoll, regex, keyGroup, valueGroup):
+ """
+ Returns the matches if the entire line matches the Regex. Returns the
+ specified groups as the key and value pair.
+
+ Args:
+ regex: the regular expression string or (re.compile) pattern.
+ keyGroup: The Regex group to use as the key. Can be int or str.
+ valueGroup: The Regex group to use the value. Can be int or str.
+ """
+ regex = Regex._regex_compile(regex)
+ return pcoll | Regex._matches_kv_object(regex=regex, keyGroup=keyGroup,
+ valueGroup=valueGroup)
+
+ @staticmethod
+ @typehints.with_input_types(str)
+ @typehints.with_output_types(str)
+ @ptransform_fn
+ def find(pcoll, regex, group=None):
+ """
+ Returns the matches if a portion of the line matches the Regex. Returns
+ the entire line (group 0 by default). Group can be integer value and a
+ string value.
+
+ Args:
+ regex: the regular expression string or (re.compile) pattern.
+ group: (optional) name of the group, it can be integer or a string value.
+ """
+ regex = Regex._regex_compile(regex)
+ group = group or 0
+
+ def _process(element):
+ r = regex.search(element)
+ if r:
+ yield r.group(group)
+ return pcoll | FlatMap(_process)
+
+ @staticmethod
+ @typehints.with_input_types(str)
+ @typehints.with_output_types(str)
+ @ptransform_fn
+ def find_all(pcoll, regex):
Review comment:
As as I read this code, for every input element, it returns the concatenated
list of all groups of all matches it found, which feels odd. E.g. consider the
regex "a(b*)" applied to "abb ax abbb". This will result in a single output
["abb", "bb", "a", "", "abbb", "bbb"].
On the other hand, the Java implementation would only return ["abb", "bb"]
(which isn't clear from its docs, and definitely doesn't match the name FindAll
let alone re.findall).
I think what makes sense here is to provide a findall() that is basically
Map(lambda line: re.findall(regex, line)) and finditer that uses finditer, and
the latter returns match objects which can be used in a follow-up lambda to
extract groups, etc. rather than a flat list of indexed groups that would be
more difficult to consume.
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Issue Time Tracking
-------------------
Worklog Id: (was: 280426)
Time Spent: 8h 40m (was: 8.5h)
> Regex transform for Python SDK
> ------------------------------
>
> Key: BEAM-7018
> URL: https://issues.apache.org/jira/browse/BEAM-7018
> Project: Beam
> Issue Type: New Feature
> Components: sdk-py-core
> Reporter: Rose Nguyen
> Assignee: Shehzaad Nakhoda
> Priority: Minor
> Time Spent: 8h 40m
> Remaining Estimate: 0h
>
> PTransorms to use Regular Expressions to process elements in a PCollection
> It should offer the same API as its Java counterpart:
> [https://github.com/apache/beam/blob/11a977b8b26eff2274d706541127c19dc93131a2/sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/Regex.java]
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