ekreutz

Ansible variable precedence

Source: http://docs.ansible.com/ansible/latest/playbooks_variables.html#variable-precedence-where-should-i-put-a-variable

From least to most important

• command line values (for example, -u my_user, these are not variables)
• role defaults (defined in role/defaults/main.yml)
• inventory file or script group vars
• inventory group_vars/all

ekreutz

Fix tmux messing with conda

Problem: When running a conda environment and opening tmux on macOS, a utility called path_helper is run again. Essentially, the shell is initialized twice which messes up the ${PATH} so that the wrong Python version shows up within tmux.

Solution

If using bash, edit /etc/profile and add one line. (For zsh, edit /etc/zprofile)

...

ekreutz

How to trim empty lines in VSCode

What this will do:

• Trim empty lines (remove all whitespace)
• Trim whitespace at the end of code lines
• Note: it will not remove any line at all, but simply trim trailing whitespace.

Steps:

1. Press Ctrl + F (Cmd + F on mac) to open the search and replace view.
2. Toggle the regex button .*.

ekreutz

from numba import njit
from numpy.typing import NDArray as array


@njit
def running_max(values: array, w: int) -> array:
    """Fast O(n) running maximum.

    For large values of `w` this solution is 100x faster or more, than the naive version.
    """

ekreutz

Convert OpenSSH private key to PEM file format

Assuming that your ssh private key is located at ~/.ssh/id_rsa. We will convert this file to the PEM format.

# Change dir to home directory
cd ~

# Make a copy of the private key and store the copy in the home directory
cp ~/.ssh/id_rsa ~/id_isa_copy

ekreutz

Naughty coroutines

Unexpected behavior when working with asyncio in Python. The behavior is likely intended, but intuitive.

import asyncio


async def fine_job(i: int):
    # A fine job that is well behaved without exceptions!

ekreutz

An antipattern in python asyncio error handling

Don't do this:

The try catch will catch any instance of SomeError, even if it's not emitted inside my_async_function. This happens if my_async_function runs for long enough so that SomeError is emitted elsewhere in the program, while this piece of code is still inside the try-except.

try:

ekreutz

Dot-product and Multi-head attention

Dot-product and Multi-head attention from the paper "Attention is all you need" (2017). Implementation in modern Tensorflow 2 using the Keras API.

Example use of the implementations below:

batch_size = 10
n_vectors = 150
d_model = 512

ekreutz

Reset SERIAL counter for a PostgreSQL database table

For the table my_table with a SERIAL column my_id.

SELECT SETVAL(
  pg_get_serial_sequence('my_table', 'my_id'),
  (SELECT COALESCE(MAX(my_id), 0) FROM my_table)
);

ekreutz

from math import log10, floor
from decimal import Decimal as Dec

# Note: the method spec uses a union type float | Dec introduced in Python 3.10
# Remove the type definitions to make it work with earlier versions.

def round_sd(x: float | Dec, sd: int = 3):
    """Round a value to a specified amount of significant digits `sd`.
    """
    return round(x, sd - int(floor(log10(abs(x)))) - 1)