﻿ Pandas: Merge two datasets using multiple join keys - w3resource # Pandas: Merge two datasets using multiple join keys

## Pandas Joining and merging DataFrame: Exercise-10 with Solution

Write a Pandas program to merge two given datasets using multiple join keys.

Test Data:

```data1:
key1 key2   P   Q
0   K0   K0  P0  Q0
1   K0   K1  P1  Q1
2   K1   K0  P2  Q2
3   K2   K1  P3  Q3
```
```data2:
key1 key2   R   S
0   K0   K0  R0  S0
1   K1   K0  R1  S1
2   K1   K0  R2  S2
3   K2   K0  R3  S3
```

Sample Solution:

Python Code :

``````import pandas as pd
data1 = pd.DataFrame({'key1': ['K0', 'K0', 'K1', 'K2'],
'key2': ['K0', 'K1', 'K0', 'K1'],
'P': ['P0', 'P1', 'P2', 'P3'],
'Q': ['Q0', 'Q1', 'Q2', 'Q3']})
data2 = pd.DataFrame({'key1': ['K0', 'K1', 'K1', 'K2'],
'key2': ['K0', 'K0', 'K0', 'K0'],
'R': ['R0', 'R1', 'R2', 'R3'],
'S': ['S0', 'S1', 'S2', 'S3']})
print("Original DataFrames:")
print(data1)
print("--------------------")
print(data2)
print("\nMerged Data:")
merged_data = pd.merge(data1, data2, on=['key1', 'key2'])
print(merged_data)
``````

Sample Output:

```Original DataFrames:
key1 key2   P   Q
0   K0   K0  P0  Q0
1   K0   K1  P1  Q1
2   K1   K0  P2  Q2
3   K2   K1  P3  Q3
--------------------
key1 key2   R   S
0   K0   K0  R0  S0
1   K1   K0  R1  S1
2   K1   K0  R2  S2
3   K2   K0  R3  S3

Merged Data:
key1 key2   P   Q   R   S
0   K0   K0  P0  Q0  R0  S0
1   K1   K0  P2  Q2  R1  S1
2   K1   K0  P2  Q2  R2  S2
```

Python Code Editor:

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## Python: Tips of the Day

How to sort a Python dict by value

Example:

```x1 = {'a': 5, 'b': 7, 'c': 9, 'd': 1}

sorted(x1.items(), key=lambda x: x)
[('d', 1), ('c', 9), ('b', 7), ('a', 5)]

# Or:

import operator
print(sorted(x1.items(), key=operator.itemgetter(1)))
```

Output:

```[('d', 1), ('a', 5), ('b', 7), ('c', 9)]
```