Implementation as class

.gitignore

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+.pytest*

README.md

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+# SoundChanger
+
+Applies sound changes to words.

soundchanger.py

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+import re
+
+
+class Change:
+    """
+    Instantiates a string representation of a sound change.
+    """
+
+    def __init__(self, change):
+        self.parse(change)
+
+    def __repr__(self):
+        return f"{self.b}>{self.a}/{self.f}_{self.t}"
+
+    def parse(self, change):
+        if '/' in change:
+            _change, _env = change.split('/')
+        else:
+            _change = change
+            _env = '_'
+        self.b, self.a = _change.split('>')
+        self.f, self.t = _env.split('_')
+        
+        if self.f.startswith("{") and self.f.endswith("}"):
+            self.f = self.f[1:-1].split(',')
+            self.f = f"[{''.join(self.f)}]"
+        if self.t.startswith("{") and self.t.endswith("}"):
+            self.t = self.t[1:-1].split(',')
+            self.t = f"[{''.join(self.t)}]"
+
+    def sub(self, string):
+        return re.sub(f"(?<={self.f}){self.b}(?={self.t})", f"{self.a}", f"#{string}#").strip('#')

tests/test_apply.py

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+from soundchanger import Change
+
+
+def test_simple_change_without_environment():
+    c = Change('p>f')
+    assert c.sub('pana') == 'fana'
+    assert c.sub('kapa') == 'kafa'
+
+def test_simple_change_with_environment():
+    c = Change('p>f/#_a')
+    assert c.sub('pana') == 'fana'
+    assert c.sub('pune') == 'pune'
+    assert c.sub('kapa') == 'kapa'
+
+def test_complex_change_with_environment():
+    c = Change('p>f/{#,a}_{a,u}')
+    assert c.sub('pana') == 'fana'
+    assert c.sub('pune') == 'fune'
+    assert c.sub('kapa') == 'kafa'
+
+# def test_simple_change_with_category():
+#     c = Change('w>h/V_V')
+#     assert c.sub('kawa') == 'kaha'
+#     assert c.sub('tuwo') == 'tuho'