﻿ NumPy: Access an array by column - w3resource

# NumPy: Access an array by column

## NumPy: Array Object Exercise-81 with Solution

Write a NumPy program to access an array by column.

Pictorial Presentation:

Sample Solution:

Python Code:

``````import numpy as np
x= np.arange(9).reshape(3,3)
print("Original array elements:")
print(x)
print("Access an array by column:")
print("First column:")
print(x[:,0])
print("Second column:")
print(x[:,1])
print("Third column:")
print(x[:,2])
```
```

Sample Output:

```Original array elements:
[[0 1 2]
[3 4 5]
[6 7 8]]
Access an array by column:
First column:
[0 3 6]
Second column:
[1 4 7]
Third column:
[2 5 8]
```

Python Code Editor:

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## Python: Tips of the Day

Python: Kwargs

**kwargs and *args are function arguments that can be very useful.

They are quite underused and often under-understood as well.

Let's try to explain what kwargs are and how to use them.

• While *args are used to pass arguments at an unknown amount to functions, **kwargs are used to do the same but with named arguments.
• So, if *args is a list being passed as an argument, you can think of **kwargs as a dictionary that's being passed as an argument to a function.
• You can use arguments as you wish as long as you follow the correct order which is: arg1, arg2, *args, **kwargs. It's okay to use only one of those but you can't mix the order, for instance, you can't have: function(**kwargs, arg1), that'd be a major faux pas in Python.
• Another example: You can do function(*args,**kwargs) since it follows the correct order.
• Here is an example. Let's say satelites are given with their names and weight in tons in dictionary format. Code prints their weight as kilograms along with their names.
```def payloads(**kwargs):
for key, value in kwargs.items():
print( key+" |||", float(value)*100)
payloads(NavSat1 = '2.5', BaysatG2 = '4')
```

Output:

```NavSat1 ||| 250.0
BaysatG2 ||| 400.0```

Since the function above would work for any number of dictionary keys, **kwargs makes perfect sense rather than passing arguments with a fixed amount.

```def payloads(**kwargs):
for key, value in kwargs.items():
print( key+" |||", float(value)*100)

sats={"Tx211":"3", "V1":"0.50"}
```Tx211 ||| 300.0