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⚡️ Speed up function _excel2num by 16% #378

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⚡️ Speed up function _excel2num by 16% #378

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20 changes: 14 additions & 6 deletions pandas/io/excel/_util.py
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Original file line number Diff line number Diff line change
Expand Up @@ -114,15 +114,23 @@ def _excel2num(x: str) -> int:
ValueError
Part of the Excel column name was invalid.
"""
index = 0
s = x.upper().strip()
if not s:
return -1

for c in x.upper().strip():
cp = ord(c)
# Precompute ord('A') for reuse
ord_A = ord("A")
ord_Z = ord("Z")
index = 0

if cp < ord("A") or cp > ord("Z"):
# Avoid redundant ord() and bounds checking in loop
for c in s:
# Fast ASCII check for latin uppercase A-Z without ord()
# CPython str is ASCII-compatible; this avoids one call to ord()
if not ("A" <= c <= "Z"):
raise ValueError(f"Invalid column name: {x}")

index = index * 26 + cp - ord("A") + 1
# Compute separately to avoid repeated calls to ord('A')
index = index * 26 + (ord(c) - ord_A + 1)

return index - 1

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