You were almost there:
facts['pop2050'] = facts.apply(lambda row: final_pop(row['population'],row['population_growth']),axis=1)
Using lambda allows you to keep the specific (interesting) parameters listed in your function, rather than bundling them in a 'row'.
Answer from Karnage on Stack OverflowGeeksforGeeks
geeksforgeeks.org โบ pandas โบ applying-lambda-functions-to-pandas-dataframe
Applying Lambda functions to Pandas Dataframe - GeeksforGeeks
July 15, 2025 - In this example, we will apply the lambda function Dataframe.assign() to a single column. The function is applied to the 'Total_Marks' column, and a new column 'Percentage' is formed with its help. ... # importing pandas library import pandas as pd # creating and initializing a list values= [['Rohan',455],['Elvish',250],['Deepak',495], ['Soni',400],['Radhika',350],['Vansh',450]] # creating a pandas dataframe df = pd.DataFrame(values,columns=['Name','Total_Marks']) # Applying lambda function to find # percentage of 'Total_Marks' column # using df.assign() df = df.assign(Percentage = lambda x: (x['Total_Marks'] /500 * 100)) # displaying the data frame df
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Applying Custom Function on Python Pandas DataFrame Columns | ...
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Applying Custom Function on Python Pandas DataFrame Columns using ...
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How do I apply a function to a pandas Series or DataFrame? - YouTube
04:23
Pandas Apply - How to Apply Lambda Functions to your DataFrames ...
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How to apply a Lambda and Function to a DataFrame column in Python ...
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Python Pandas Lambda Function Tutorial With EXAMPLES - YouTube
Pandas
pandas.pydata.org โบ docs โบ reference โบ api โบ pandas.DataFrame.apply.html
pandas.DataFrame.apply โ pandas 3.0.6 documentation
Passing result_type='broadcast' will ensure the same shape result, whether list-like or scalar is returned by the function, and broadcast it along the axis. The resulting column names will be the originals. >>> df.apply(lambda x: [1, 2], axis=1, result_type="broadcast") A B 0 1 2 1 1 2 2 1 2 ยท Advanced users can speed up their code by using a Just-in-time (JIT) compiler with apply. The main JIT compilers available for pandas are Numba and Bodo.
Top answer 1 of 4
40
You were almost there:
facts['pop2050'] = facts.apply(lambda row: final_pop(row['population'],row['population_growth']),axis=1)
Using lambda allows you to keep the specific (interesting) parameters listed in your function, rather than bundling them in a 'row'.
2 of 4
32
Your function,
def function(x):
// your operation
return x
call your function as,
df['column']=df['column'].apply(function)
Arabpsychology
statistics.arabpsychology.com โบ psychological statistics โบ learning pandas: applying custom functions with lambda expressions
Learning Pandas: Applying Custom Functions With Lambda Expressions - PSYCHOLOGICAL STATISTICS
October 29, 2025 - When paired, .apply() uses the lambda function to define the operation performed on each item of the Series. This pairing allows for incredibly expressive and efficient inline application of custom logic. Consider the general syntax for applying conditional logic to a Pandas Series, where the ...
Pandas
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pandas.Series.apply โ pandas 3.0.6 documentation - PyData |
Square the values by passing an anonymous function as an argument to apply(). >>> s.apply(lambda x: x**2) London 400 New York 441 Helsinki 144 dtype: int64 ยท Define a custom function that needs additional positional arguments and pass these additional arguments using the args keyword.
GeeksforGeeks
geeksforgeeks.org โบ python โบ apply-a-function-to-each-row-or-column-in-dataframe-using-pandas-apply
Apply a function to each row or column in Dataframe using pandas.apply() - GeeksforGeeks
July 15, 2025 - In this example, weโll apply a lambda function that adds 10 to each value in every column of the DataFrame. ... import pandas as pd import numpy as np # Creating a list of tuples for the DataFrame matrix = [(1, 2, 3, 4), (5, 6, 7, 8), (9, 10, 11, 12), (13, 14, 15, 16)] # Creating the DataFrame df = pd.DataFrame(matrix, columns=list('abcd')) # Output the DataFrame print("Original DataFrame:") print(df) print('\n') # Applying lambda function to add 10 to each value in every column new_df = df.apply(lambda x: x + 10) print("New DataFrame:") print(new_df)
Top answer 1 of 8
712
Given a sample dataframe df as:
a b
0 1 2
1 2 3
2 3 4
3 4 5
what you want is:
df['a'] = df['a'].apply(lambda x: x + 1)
that returns:
a b
0 2 2
1 3 3
2 4 4
3 5 5
2 of 8
163
For a single column better to use map(), like this:
df = pd.DataFrame([{'a': 15, 'b': 15, 'c': 5}, {'a': 20, 'b': 10, 'c': 7}, {'a': 25, 'b': 30, 'c': 9}])
a b c
0 15 15 5
1 20 10 7
2 25 30 9
df['a'] = df['a'].map(lambda a: a / 2.)
a b c
0 7.5 15 5
1 10.0 10 7
2 12.5 30 9
VDCI
vdci.edu โบ transforming dataframes with apply and lambda functions
Transforming DataFrames with Apply and Lambda Functions - Free Video Tutorial
May 19, 2025 - Create a DataFrame with a "numbers" column from 10,000 to 10,010 and transform it using apply with functions (like add_five and add_sets), then chain them or replace with lambda functions for concise transformations. ... Learn how to efficiently transform data in a Pandas DataFrame using the apply function to run custom transformations on each item in a column.
Statology
statology.org โบ home โบ pandas: how to use apply & lambda together
Pandas: How to Use Apply & Lambda Together
June 23, 2022 - #modify existing 'points' column df['points'] = df['points'].apply(lambda x: x/2 if x < 20 else x*2) #view updated DataFrame print(df) team points assists 0 A 9.0 5 1 B 44.0 7 2 C 9.5 7 3 D 7.0 9 4 E 7.0 12 5 F 5.5 9 6 G 40.0 9 7 H 56.0 4 ยท In this example, we modified the values in the existing points column by using the following rule in the lambda function:
Pandas
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pandas.Series.apply โ pandas 2.2.2 documentation - PyData |
Square the values by passing an anonymous function as an argument to apply(). >>> s.apply(lambda x: x**2) London 400 New York 441 Helsinki 144 dtype: int64 ยท Define a custom function that needs additional positional arguments and pass these additional arguments using the args keyword.
Stack Exchange
datascience.stackexchange.com โบ questions โบ 75556 โบ update-a-pandas-data-frame-column-using-apply-lambda-and-group-by-functions
python - Update a pandas data frame column using Apply,Lambda and Group by Functions - Data Science Stack Exchange
June 6, 2020 - I used 'Apply' function to every row in the pandas data frame and created a custom function to return the value for the 'Candidate Won' Column using data frame,row-level 'Constituency','% of Votes' Custom Function Code: def update_candidateresult(df,a,b): max_voteshare=df.groupby(df['Constituency']==a)['% of Votes'].max()[True] if b==max_voteshare: return "won" else: return "loss" Final Code : df_andhrapradesh['Candidate Won']=df_andhrapradesh.apply(lambda row:update_candidateresult(df_andhrapradesh,row['Constituency'],row['% of Votes']),axis=1) Share ยท