Merge pull request #13 from ZeroGachis/task/implement-left-strip

✨ Add left-strip preprocessor

README.md

@@ -111,6 +111,7 @@ assert rows == [{"name": "Joe"}, {"name": "William"}, {"name": "Jack"}, {"name":
 - regex-extract
 - replace
 - strip-whitespaces
+- left-strip
 
 #### Validators
 

magicparse/pre_processors.py

@@ -73,6 +73,18 @@ def key() -> str:
         return "strip-whitespaces"
 
 
+class LeftStrip(PreProcessor):
+    def __init__(self, characters: str) -> None:
+        self.characters = characters
+
+    def apply(self, value: str) -> str:
+        return value.lstrip(self.characters)
+
+    @staticmethod
+    def key() -> str:
+        return "left-strip"
+
+
 class RegexExtract(PreProcessor):
     def __init__(self, pattern: str) -> None:
         pattern = re.compile(pattern)
@@ -97,4 +109,4 @@ def key() -> str:
         return "regex-extract"
 
 
-builtins = [LeftPadZeroes, Map, RegexExtract, Replace, StripWhitespaces]
+builtins = [LeftPadZeroes, Map, RegexExtract, Replace, StripWhitespaces, LeftStrip]

tests/test_pre_processors.py

@@ -6,6 +6,7 @@
     RegexExtract,
     Replace,
     StripWhitespaces,
+    LeftStrip,
 )
 import pytest
 from unittest import TestCase
@@ -38,6 +39,12 @@ def test_strip_whitespaces(self):
         pre_processor = PreProcessor.build({"name": "strip-whitespaces"})
         assert isinstance(pre_processor, StripWhitespaces)
 
+    def test_left_strip(self):
+        pre_processor = PreProcessor.build(
+            {"name": "left-strip", "parameters": {"characters": "0"}}
+        )
+        assert isinstance(pre_processor, LeftStrip)
+
     def test_regex_extract(self):
         pre_processor = PreProcessor.build(
             {
@@ -114,6 +121,20 @@ def test_success(self):
         assert pre_processor.apply("    an input     ") == "an input"
 
 
+class TestLeftStrip(TestCase):
+    def test_do_nothing(self):
+        pre_processor = PreProcessor.build(
+            {"name": "left-strip", "parameters": {"characters": "0"}}
+        )
+        assert pre_processor.apply("12345") == "12345"
+
+    def test_success(self):
+        pre_processor = PreProcessor.build(
+            {"name": "left-strip", "parameters": {"characters": "0"}}
+        )
+        assert pre_processor.apply("0000012345") == "12345"
+
+
 class TestRegexExtract(TestCase):
     def test_build_without_value_group(self):
         with pytest.raises(