如何在Python Pandas中加入CSV比较2 CSV

Question

I have 2 csv files lets say A.csv and B.csv . A.csv has columns a,b,c,d and B.csv has columns x,y,z,t. I want to search that if an entry in column a exist in column x then print z and d if that rows.

Like,

for each i in A
    if A.[a][i] exist in B.x
       print A.[d][i] + B.[z][i]

-- I have already the code below. I just need to learn how to settle the code for this

 import pandas as pd
 import numpy as np
 import matplotlib.pyplot as plt


A = pd.read_csv('path1')
B = pd.read_csv('path2')

Answer 1

Imagine your csv data file looks like below:

print(df1)

    A   B   C   D
0   1   4   7   4
1   2   5   8   5
2   3   6   9   8

print(df2

    X   Y   Z   T
0   1   11  6   8
1   5   12  8   0
2   2   13  0   4

A simple merge would solve your problem, considering Left table is df1 and Right is df2

df  = df1.merge(df2,left_on='A',right_on='X')[['Z','D']]

print(df)

    Z   D
0   6   4
1   0   5

This will return the matched row elements from mentioned columns. (here Z,D)

Answer 2

I think the simplest solution is to use a left join:

>>> print(A)
   a  b  c  d
0  1  2  3  4
1  2  3  4  5
2  4  4  5  6

>>> print(B)

   x   y   z   t
0  1  20  30  40
1  3   4   5   6

>>> result = A.merge(left_on='a', right=B, right_on='x', how='left')[['z', 'd']].dropna()

>>> print(result)
      z  d
0  30.0  4