STYLE/PERF: use f-strings instead of ''.join on static elements (#49517)

STYLE: use f-strings instead of ''.join on static elements

Author: akx

Diff for: pandas/core/apply.py

@@ -1287,9 +1287,7 @@ def _make_unique_kwarg_list(
     [('a', '<lambda>_0'), ('a', '<lambda>_1'), ('b', '<lambda>')]
     """
     return [
-        (pair[0], "_".join([pair[1], str(seq[:i].count(pair))]))
-        if seq.count(pair) > 1
-        else pair
+        (pair[0], f"{pair[1]}_{seq[:i].count(pair)}") if seq.count(pair) > 1 else pair
         for i, pair in enumerate(seq)
     ]
 

Diff for: 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"

Diff for: pandas/io/formats/css.py

@@ -194,11 +194,11 @@ class CSSResolver:
 
     CSS_EXPANSIONS = {
         **{
-            "-".join(["border", prop] if prop else ["border"]): _border_expander(prop)
+            (f"border-{prop}" if prop else "border"): _border_expander(prop)
             for prop in ["", "top", "right", "bottom", "left"]
         },
         **{
-            "-".join(["border", prop]): _side_expander("border-{:s}-" + prop)
+            f"border-{prop}": _side_expander(f"border-{{:s}}-{prop}")
             for prop in ["color", "style", "width"]
         },
         **{