Author: John Au-Yeung

Sometimes, we want to run a shell command and capturing the output with Python.

In this article, we’ll look at how to run a shell command and capturing the output with Python.

How to run a shell command and capturing the output with Python?

To run a shell command and capturing the output with Python, we can use the subprocess.run method.

For instance, we write:

import subprocess

result = subprocess.run(['ls', '-l'], stdout=subprocess.PIPE)
print(result.stdout)

We call subprocess.run with an array that has the command string with its arguments.

And we set stdout to subprocess.PIPE to pipe the input to stdout.

We then get the output from the result.stdout property as a binary string.

As a result, we get something like:

b'total 28\n-rw-r--r-- 1 runner runner    5 Oct 16 20:15 file\n-rw-r--r-- 1 runner runner   13 Oct 16 01:41 foo.txt\n-rw-r--r-- 1 runner runner  102 Oct 17 01:58 main.py\n-rw-r--r-- 1 runner runner 4540 Oct 16 22:17 photo.jpg\n-rw-r--r-- 1 runner runner 3449 Oct 16 22:24 poetry.lock\ndrwxr-xr-x 1 runner runner   36 Oct 15 23:31 __pycache__\n-rw-r--r-- 1 runner runner  358 Oct 16 22:24 pyproject.toml\n'

as the value of result.stdout.

Conclusion

To run a shell command and capturing the output with Python, we can use the subprocess.run method.

Sometimes, we want to get all possible combinations of a list’s elements with Python.

In this article, we’ll look at how to get all possible combinations of a list’s elements with Python.

How to get all possible combinations of a list’s elements with Python?

To get all possible combinations of a list’s elements with Python, we can use the itertools.combinations method.

For instance, we write:

import itertools

stuff = [1, 2, 3]
for L in range(0, len(stuff) + 1):
    for subset in itertools.combinations(stuff, L):
        print(subset)

We loop through number ranges from 0 to len(stuff) + 1.

In the loop body, we get the combination of stuff when we choose L items with itertools.combinations.

And then we loop through the returned iterator with another for loop.

In the loop body, we print the subset of items from stuff that are chosen, which are stored in a tuple.

Therefore, we see:

()
(1,)
(2,)
(3,)
(1, 2)
(1, 3)
(2, 3)
(1, 2, 3)

printed.

Conclusion

To get all possible combinations of a list’s elements with Python, we can use the itertools.combinations method.

Sometimes, we want to generate all permutations of a list with Python.

In this article, we’ll look at how to generate all permutations of a list with Python.

How to generate all permutations of a list with Python?

To generate all permutations of a list with Python, we can use the itertools.permutations method.

For instance, we write:

import itertools

perms = list(itertools.permutations([1, 2, 3]))
print(perms)

We call itertools.permtations with a list to get all the permutations from.

It returns a iterator with all the permutations of [1, 2, 3].

Next, we convert the iterator to a list with list and assign it to perms.

Therefore, perms is:

[(1, 2, 3), (1, 3, 2), (2, 1, 3), (2, 3, 1), (3, 1, 2), (3, 2, 1)]

Conclusion

To generate all permutations of a list with Python, we can use the itertools.permutations method.

Sometimes, we want to determine the encoding of text with Python.

In this article, we’ll look at how to determine the encoding of text with Python.

How to determine the encoding of text with Python?

To determine the encoding of text with Python, we can use the python-magic package.

To install it, we run:

pip install python-magic

Then we write:

import magic

blob = open('foo.txt', 'rb').read()
m = magic.open(magic.MAGIC_MIME_ENCODING)
m.load()
encoding = m.buffer(blob)
print(encoding)

to open the foo.txt file with open.

Then we read the file with read.

Next, we call magic.open with magic.MAGIC_MIME_ENCODING and assign the returned object to m to let us call the load and buffer methods to determine the encoding of blob`.

blob has the returned file handle from read.

Conclusion

To determine the encoding of text with Python, we can use the python-magic package.

Sometimes, we want to get the key with maximum value in dictionary with Python.

In this article, we’ll look at how to get the key with maximum value in dictionary with Python.

How to get the key with maximum value in dictionary with Python?

To get the key with maximum value in dictionary with Python, we can use the max method with the key set to the get method of the dictionary.

For instance, we write:

stats = {'a': 1000, 'b': 3000, 'c': 100}
max_stats = max(stats, key=stats.get)
print(max_stats)

to call max with the stats dictionary and key set to stats.get, which returns the value of the entry with the given key.

And then we assign the returned value to max_stats.

Therefore, max_stats is 'b'.

Conclusion

To get the key with maximum value in dictionary with Python, we can use the max method with the key set to the get method of the dictionary.