Fluent interfaces technically return self or this from each chained function. Pandas returns new instances of the same type. Technically, that isn't fluent. I suspect it is meant to be indistinguishable for optimization reasons.

isitfluent.py

#!/usr/bin/env python

import pandas as pd


def getDataframe(url_table, ind):
    df = pd.read_html(url_table)[ind]
    return df


# Chaining functions
df = (
    getDataframe("https://en.wikipedia.org/wiki/Historical_population_of_Ireland", 1)
    .drop(columns=["Rank"])
    .rename(columns=lambda x: x.lower())
    .query("province == 'Leinster'")
    .sort_values("density (/ km2)", ascending=True)
)

print(df)


# But, is this a fluent interface? It creates new objects each time
df = getDataframe("https://en.wikipedia.org/wiki/Historical_population_of_Ireland", 1)
print(id(df))
df = df.drop(columns=["Rank"])
print(id(df))
df = df.rename(columns=lambda x: x.lower())
print(id(df))
df = df.query("province == 'Leinster'")
print(id(df))
df = df.sort_values("density (/ km2)", ascending=True)
print(id(df))