Category: Python Answers

Sometimes, we want to find the index of an item in a list with Python.

In this article, we’ll look at how to find the index of an item in a list with Python.

How to find the index of an item in a list with Python?

To find the index of an item in a list with Python, we can use the index method available in a Python array.

For instance, we write:

index = ["foo", "bar", "baz"].index("bar")
print(index)

We call index with the value we’re looking for.

And the index of the first element with the given value is returned.

Therefore index is 1.

Conclusion

To find the index of an item in a list with Python, we can use the index method available in a Python array.

Sometimes, we want to make a flat list out of a list of lists with Python.

In this article, we’ll look at how to make a flat list out of a list of lists with Python.

How to make a flat list out of a list of lists with Python?

To make a flat list out of a list of lists with Python, we can use the sum function.

For instance, we write:

sublist = [[1, 2, 3], [4, 5, 6], [7], [8, 9]]
flat_list = sum(sublist, [])
print(flat_list)

We call sum with sublist and an empty array to put all the entries of the nested arrays into the empty array and return it.

Therefore flat_list is [1, 2, 3, 4, 5, 6, 7, 8, 9].

Conclusion

To make a flat list out of a list of lists with Python, we can use the sum function.

Sometimes, we want to access the index in Python for loops.

In this article, we’ll look at how to access the index in Python for loops.

How to access the index in Python for loops?

To access the index in Python for loops, we can use the enumerate function.

For instance, we write:

ints = [100, 200, 300]
for idx, val in enumerate(ints):
    print(idx, val)

to call enumerate with the ints array to return an array with the idx and val tuples.

idx is the index of the array entry.

val is the value of the array entry.

Therefore, we see:

0 100
1 200
2 300

logged as a result.

Conclusion

To access the index in Python for loops, we can use the enumerate function.

Sometimes, we want to safely create a nested directory in Python.

In this article, we’ll look at how to safely create a nested directory in Python.

How to safely create a nested directory in Python?

To safely create a nested directory in Python, we can use the Path instance’s mkdir method.

For instance, we write:

from pathlib import Path
Path("./my/directory").mkdir(parents=True, exist_ok=True)

We invoke the Path constructor with the path of the directory we want to create.

Then we set parents and exist_ok to True so that it’ll create the nested directory without the parent directory being present.

Conclusion

To safely create a nested directory in Python, we can use the Path instance’s mkdir method.

Sometimes, we want to execute a program or call a system command with Python.

In this article, we’ll look at how to execute a program or call a system command with Python.

How to execute a program or call a system command with Python?

To execute a program or call a system command with Python, we can use the subprocess.run method.

For instance, we write:

import subprocess
subprocess.run(["ls", "-l"])

We pass in an array with the command as the first entry.

And the options are in the subsequent entries.

Now we should see the listings of the content of the current working directory displayed.

Conclusion

To execute a program or call a system command with Python, we can use the subprocess.run method.