dpapathanasiou

SchemaSpy is a neat tool to produce visual diagrams for most relational databases.

Here's how to use it to generate schema relationship diagrams for PostgreSQL databases:

1. Download the jar file from here (the current version is v6.1.0)

2. Get the PostgreSQL JDBC driver (unless your installed version of java is really old, use the latest JDBC4 jar file)

3. Run the command against an existing database. For most databases, the schema (-s option) we are interested in is the public one:

dpapathanasiou

from datetime import datetime
import pytz

def is_dst ():
    """Determine whether or not Daylight Savings Time (DST)
    is currently in effect"""

    x = datetime(datetime.now().year, 1, 1, 0, 0, 0, tzinfo=pytz.timezone('US/Eastern')) # Jan 1 of this year
    y = datetime.now(pytz.timezone('US/Eastern'))

dpapathanasiou

No fuss Julia and Jupyter Notebook setup on macOS and linux

After installing julia (using the standard curl ... | sh approach), this one-liner does all the project dependency installs, given the existence of a Project.toml file at .:

julia --project=. -e "using Pkg; Pkg.instantiate()"

Then, this one-liner runs jupyter within a new conda environment, which is completely self-contained within julia (i.e., no need to install conda first and create a new environment for this project):

dpapathanasiou

/* This is a scala solution for a mini domain specific language (DSL)
 * defining instructions for populating an empty matrix.
 * 
 * Input consists of a single string separated by spaces:
 * - the first number represents the size of the matrix, NxN
 * - the rest of the input consists of one or more strings defining
 *   the range of cells and how each of their populations will be
 *   incremented
 * 
 * Increment pattern possibilities:

dpapathanasiou

This is a simple way of using the real time json format feed from the Port Authority Trans-Hudson (PATH) rail system to get a list of when the next trains are arriving per station.

This gist uses both curl and jq, which are typically pre-installed on most computers.

curl -s https://www.panynj.gov/bin/portauthority/ridepath.json | \
jq -r \
--arg STATION "HOB" \
'.results[] | select (.consideredStation == $STATION) | .destinations[] | .messages[] | (.arrivalTimeMessage | (" " * (8 - length)) +.)  + " => " + .headSign' 

dpapathanasiou

Based on the Host communication instructions, but with a tweak for when the usb0 address is not found:

$ /sbin/ip link set usb0 up
Cannot find device "usb0"

Because of the predictable network interface name scheme, though, usb0 may be renamed to something else:

dpapathanasiou

#!/usr/bin/env python

"""
A breadth-first search implementation from:

"Python Algorithms: Mastering Basic Algorithms in the Python Language"

by  	Magnus Lie Hetland

ISBN: 	9781484200551 

dpapathanasiou

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dpapathanasiou

Rationale

The Raspberry Pi Model A+ has just a single usb port, so getting the wifi configured has to done by editing /etc/network/interfaces from a command line prompt.

These instructions assume the Raspbian OS on the SD card, and a usb wifi adapter that supports the RTL8192cu chipset, since the current Raspbian has built-in support for it.

Before the first boot

1. Put a keyboard in the usb slot
2. Connect the HDMI slot to a monitor

dpapathanasiou

Create the Certificate Signing Request (CSR) file

openssl req -nodes -newkey rsa:4096 -keyout example_com.key -out example_com.csr

Prepare the Bundle file

Unzip the file Comodo sends back and create a single certificate bundle file.