CLN: replace joins on static arguments with f-strings

Author: akx

pandas/core/apply.py

@@ -1355,7 +1355,7 @@ def _make_unique_kwarg_list(
     [('a', '<lambda>_0'), ('a', '<lambda>_1'), ('b', '<lambda>')]
     """
     return [
-        (pair[0], "_".join([pair[1], str(seq[:i].count(pair))]))
+        (pair[0], f"{pair[1]}_{seq[:i].count(pair)}")
         if seq.count(pair) > 1
         else pair
         for i, pair in enumerate(seq)

pandas/core/window/doc.py

@@ -10,7 +10,7 @@
 
 def create_section_header(header: str) -> str:
     """Create numpydoc section header"""
-    return "\n".join((header, "-" * len(header))) + "\n"
+    return f"{header}\n{'-' * len(header)}\n"
 
 
 template_header = "\nCalculate the {window_method} {aggregation_description}.\n\n"