MyPythoncode converts latitude and longitude using pyproj. It reads this from an existing CSV file and writes a new CSV file with new code.

When it comes across a blank cell within the existing CSV file it writes in the cell of the new CSV file 'inf'

How can I stop it writing anything and leave the cell blank?

Current Python Code

from pyproj import Transformer
import pandas

pdf = pandas.read_csv("existing_file.csv", encoding='ANSI')
transformer = Transformer.from_crs("epsg:99999", "epsg:8888", always_xy=True)
xx, yy = transformer.transform(pdf["longitude"].values, pdf["latitude"].values)
pdf = pdf.assign(longitude=xx, latitude=yy)
pdf.to_csv("new_file.csv")