I am writing a custom error message when 2 Pandas series are not equal and want to use '<' to point at the differences.

Here's the workflow for a failed equality:

1. Convert both lists to Python: pd.Series([list])
2. Side by side comparison in a dataframe: table = pd.concat([list1], [list2]), axis=1
3. Add column and index names: table.columns = ['...', '...'], table.index = ['...', '...']

Current output:

|Yours|Actual|

|1|1|

|2|2|

|4|3|

Desired output:

|Yours|Actual|-|

|1|1||

|2|2||

|4|3|<|

The naive solution is iterating through each list index and if it's not equal, appending '<' to another list then putting this list into pd.concat() but I am looking for a method using Pandas. For example,

error_series = '<' if (abs(yours - actual) >= 1).all(axis=None) else ''

Ideally it would append '<' to a list if the difference between the results is greater than the Margin of Error of 1, otherwise append nothing

Note: Removed tables due to StackOverflow being picky and not letting my post my question

CodePudding user response：

You can create the DF and give index and column names in one line:

import pandas as pd
list1 = [1,2,4]
list2 = [1,2,10]
df = pd.DataFrame(zip(list1, list2), columns=['Yours', 'Actual'])

Create a boolean mask to find the rows that have a too large difference:

margin_of_error = 1
mask = df.diff(axis=1)['Actual'].abs()>margin_of_error

Add a column to the DF and set the values of the mask as you want:

df['too_different'] = df.diff(axis=1)['Actual'].abs()>margin_of_error
df['too_different'].replace(True, '<', inplace=True)
df['too_different'].replace(False, '', inplace=True)

output:

   Yours  Actual too_different
0      1       1              
1      2       2              
2      4      10             <

CodePudding user response：

or you can do something like this:

df = df.assign(diffr=df.apply(lambda x: '<' 
                              if (abs(x['yours'] - x['actual']) >= 1) 
                              else '', axis=1))
print(df)
'''
   yours  actual diffr
0      1       1      
1      2       2      
2      4       3     <