Python Pandas Commands .replace() Not Working despite inplace = True

Question

I’m trying to use .replace() on a DataFrame made from .read_excel(). The command is not working despite using inplace = True, and triple-checking the spelling (copy pasted from original excel doc)

import pandas as pd

def create_frame(path):
    df1 = pd.read_excel(path)
    return df1.replace(('Visit 2: Day 1','Day 1'), inplace = True)

df = create_frame('example.xlsx')
df.to_csv('test.csv')

i’ve also tried using df2 = df1.replace(('Visit 2: Day 1','Day 1')) instead of using inplace = True but the test csv always comes out with ‘Visit 2: Day 1’

I’m having a similar dysfunction (commands not working) with .sort_values and .reset_index as well.

Any ideas what i’m doing wrong? All help is appreciated! thank you!

Asked By: Oliver

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Source

Answer 1

You can create the function create_frame without inplace=True.

if you use inplace=True, it will return None from the func create_frame.

similarly, Pandas dataframe: set_index with inplace=True returns a NoneType, why??

import pandas as pd

def create_frame(path):
    df1 = pd.read_excel(path)
    return df1.replace(('Visit 2: Day 1','Day 1'))

df = create_frame('example.xlsx')
df.to_csv('test.csv')

when you use df2 = df1.replace(('Visit 2: Day 1','Day 1')), it will not affect df1.

so without use func, you can do like this:

df1 = pd.read_excel(path)
df2 = df1.replace(('Visit 2: Day 1','Day 1'))
df2.to_csv('test.csv')

df1 = pd.read_excel(path)
df1.replace(('Visit 2: Day 1','Day 1'), inplace=True)
df1.to_csv('test.csv')

Answered By: Ferris

Answer 2

I have had the same issue, and Ferris suggestion is the only way it worked for me.

I’m using your suggestion and try to loop it through a folder containing ~100 files.
I’m new to programming and currently writing my thesis. Do you @Ferris have a suggestion on how to loop this function?

Answered By: Kristina Cvetanoska

Python Pandas Commands .replace() Not Working despite inplace = True

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