Update word_frequency_functions.py

Author: cclauss

machine_learning/word_frequency_functions.py

@@ -75,14 +75,14 @@ def document_frequency(term: str, corpus: str) -> int:
 the third document in the corpus.")
     (1, 3)
     """
-    corpus_without_punctuation = corpus.translate(
+    corpus_without_punctuation = corpus.lower().translate(
         str.maketrans("", "", string.punctuation)
     )  # strip all punctuation and replace it with ''
-    documents = corpus_without_punctuation.split("\n")
-    lowercase_docs = [document.lower() for document in documents]
+    docs = corpus_without_punctuation.split("\n")
+    term = term.lower()
     return (
-        len([doc for doc in lowercase_docs if term.lower() in doc]),
-        len(documents),
+        len([doc for doc in docs if term in doc]),
+        len(docs),
     )