Regardless of the performance, you should be able to do this using loc with boolean indexing:
df = pd.DataFrame([[5, 2], [3, 4]], columns=('a', 'b'))
# modify value in column b where a is 3
df.loc[df.a == 3, 'b'] = 6
df
# a b
#0 5 2
#1 3 6
Answer from akuiper on Stack OverflowPandas
pandas.pydata.org โบ pandas-docs โบ stable โบ reference โบ api โบ pandas.DataFrame.replace.html
pandas.DataFrame.replace โ pandas 3.0.6 documentation
Replace values given in to_replace with value. Values of the Series/DataFrame are replaced with other values dynamically.
Statology
statology.org โบ home โบ how to replace values in a pandas dataframe (with examples)
How to Replace Values in a Pandas DataFrame (With Examples)
September 27, 2022 - The following code shows how to replace multiple values in an entire pandas DataFrame: #replace 'E' with 'East' and 'W' with 'West' df = df.replace(['E', 'W'],['East', 'West']) #view DataFrame print(df) team division rebounds 0 A East 11 1 A West 8 2 B East 7 3 B East 6 4 B West 6 5 C West 5 6 C East 12 ยท The following code shows how to replace a single value in a single column:
python - Replace single value in a pandas dataframe, when index is not known and values in column are unique - Stack Overflow
There is a question on SO with the title "Set value for particular cell in pandas DataFrame", but it assumes the row index is known. How do I change a value, if the row values in the relevant colum... More on stackoverflow.com
python - Trying to change a single value in pandas dataframe - Stack Overflow
I've seen a bunch of questions with similar titles but I still cant figure it out. All I want to do is replace the value thats in my dataframe in the fifth row and 5th column with the value 100. I More on stackoverflow.com
How to replace a particular Pandas dataframe value by location?
Check out this SO answer, the recommended way is to use pandas.DataFrame.set_value: DataFrame.set_value(index, col, value, takeable=False) Put single value at passed column and index So in your case this would be df.set_value(0, 'dog', 'dog11'). More on reddit.com
python - How do i replace the value of a data-frame column with a single value? - Stack Overflow
Domain expertise still wanted: the latest trends in AI-assisted knowledge for... ... Iโm Jody, the Chief Product and Technology Officer at Stack Overflow. Letโs... 4 Pandas DataFrame, replace value of a column by the value of an other column ยท 0 How to find and replace a single value in ... More on stackoverflow.com
Python Course
python-course.eu โบ numerical-programming โบ accessing-and-changing-values-dataframes.php
27. Accessing and Changing values of DataFrames | python-course.eu
So we have to change our DataFrame accodingly: df.replace("programmer", "computer scientist", inplace=True) df ยท to_replace can be a list consisting of str, regex or numeric objects. If both the values of to_replace and value are both lists, they must be the same length.
Top answer 1 of 2
25
.loc is an indexer. It looks for an entry in the index, but the column name is not an index. It is simply a column. The following solutions would work:
df.loc[4, 'rating'] = 100 # Because 4 is in the index, but how do you know?
or:
df.loc[df['name']=='cheerio', 'rating'] = 100 # Find the row by column
or:
df.set_index('name', inplace=True) # Make 'name' the index
df.loc['cheerios', 'rating'] = 100 # Use the indexer
2 of 2
1
Try using pandas.DataFrame.at:
df.at[df['name'].tolist().index('cherrio'),'rating']=100
print(df)
Output:
name sugar sodium rating
0 fruit loop x x x
1 trix x x x
2 oreo x x x
3 cocoa puff x x x
4 cheerio x x 100
Data to Fish
datatofish.com โบ replace-values-pandas-dataframe
How to Replace Values in a pandas DataFrame
In this tutorial, you will learn how to replace values in a DataFrame.
Reddit
reddit.com โบ r/learnpython โบ how to replace a particular pandas dataframe value by location?
r/learnpython on Reddit: How to replace a particular Pandas dataframe value by location?
June 30, 2016 -
I have the following pandas DataFrame.
import pandas as pd
df = pd.read_csv('filename.csv')
print(df)
dog A B C
0 dog1 0.787575 0.159330 0.053095
1 dog10 0.770698 0.169487 0.059815
2 dog11 0.792689 0.152043 0.055268
3 dog12 0.785066 0.160361 0.054573
4 dog13 0.795455 0.150464 0.054081
5 dog14 0.794873 0.150700 0.054426
.. ....
8 dog19 0.811585 0.140207 0.048208
9 dog2 0.797202 0.152033 0.050765
10 dog20 0.801607 0.145137 0.053256
11 dog21 0.792689 0.152043 0.055268
....I know for row 0 and in column df['dog'], the first value needs to be explicitly changed. Instead of dog1, it should be dog11.
What are all the ways a user can change this value?
Top answer 1 of 2
2
Check out this SO answer, the recommended way is to use pandas.DataFrame.set_value: DataFrame.set_value(index, col, value, takeable=False) Put single value at passed column and index So in your case this would be df.set_value(0, 'dog', 'dog11').
2 of 2
2
df.loc uses the row/column names df.loc[0, 'dog'] = 'dog1' df.iloc uses row/column indices df.iloc[0, 0] = 'dog1' Lots of good info in the docs: http://pandas.pydata.org/pandas-docs/stable/indexing.html Apparently if you're just setting a single value there is also df.at and df.iat which are faster.
PythonForBeginners.com
pythonforbeginners.com โบ home โบ pandas replace value in a dataframe
Pandas Replace Value in a Dataframe - PythonForBeginners.com
January 4, 2023 - After execution, the replace() ... to replace different values in different columns with a single final value, you can pass a dictionary to the replace() method as the first input argument....