How to print rolling window equation process from pandas dataframe in python?

问题

I created a pandas dataframe sample and it tried to sum for every 3 rows:

import pandas as pd
import numpy as np

d={'A':[100,110,120,175,164,169,155,153,156,200]}
df=pd.DataFrame(d)

     A
0  100
1  110
2  120
3  175
4  164
5  169
6  155
7  153
8  156
9  200

0      NaN
1      NaN
2    330.0 #this is the result tho
3    405.0
4    459.0
5    508.0
6    488.0
7    477.0
8    464.0
9    509.0
Name: sum, dtype: float64

And i want to display the equation process like this:

   NaN
   NaN
   330.0 = 100+110+120
   405.0 = 110+120+175
   459.0      .
   508.0      .
   488.0      .
   477.0      .   
   464.0      .
   509.0     etc.

Here's the code that i tried with for loop:

for i in range(len(total)):
    print("{}={}+{}+{}".format(total[i],"a","b","c"))

nan=a+b+c
nan=a+b+c
330.0=a+b+c
405.0=a+b+c
459.0=a+b+c
508.0=a+b+c
488.0=a+b+c
477.0=a+b+c
464.0=a+b+c
509.0=a+b+c

PS: a, b, and c replaced with the number from the dataframe

I don't know if it possible with pandas library or just do it with python library only. I'm just curious

回答1:

d={'A':[100,110,120,175,164,169,155,153,156,200]}
df=pd.DataFrame(d)
for ind in df.index:
        if ind == 0 or ind == 1:
            print("NaN")
        else:
            sumOf3Numbers = df["A"][ind-2]+df["A"][ind-1]+df["A"][ind]
            print("{}={}+{}+{}".format(sumOf3Numbers,df["A"][ind-2],df["A"][ind-1],df["A"][ind]))

回答2:

It's a little bit tricky to get rolling to work with conditional string output

equations = []
df.A.rolling(3).apply(lambda x: equations.append(f'{x.sum()} = {x.iloc[0]}+{x.iloc[1]}+{x.iloc[2]}') or 0)
df.loc[2:, 'equations'] = equations
print(df)

Out:

     A                  equations
0  100                        NaN
1  110                        NaN
2  120  330.0 = 100.0+110.0+120.0
3  175  405.0 = 110.0+120.0+175.0
4  164  459.0 = 120.0+175.0+164.0
5  169  508.0 = 175.0+164.0+169.0
6  155  488.0 = 164.0+169.0+155.0
7  153  477.0 = 169.0+155.0+153.0
8  156  464.0 = 155.0+153.0+156.0
9  200  509.0 = 153.0+156.0+200.0

来源：https://stackoverflow.com/questions/64089678/how-to-print-rolling-window-equation-process-from-pandas-dataframe-in-python

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python

pandas

dataframe