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from sqlalchemy.ext.declarative import declarative_base

"""
This gist demonstrates ways to retrieve foreign keys in an SQLAlchemy database schema.
"""

Base = declarative_base()
metadata = Base.metadata

# then you must populate schema

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#! /bin/bash
#log memory each minute
while true; do
dt=`date`
mem=`cat /proc/meminfo | grep -E "MemFree"`
mem2=`cat /proc/meminfo | grep -E "MemAvailable"`
echo -e "$dt \t $mem \t $mem2" | tee -a memlog.txt
sleep 60
done

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"""
This contains various implementations of SQL functions in python
The two functions are not built for the same context
"""

def hash_join(table1, index1, table2, index2):
    """
    Perform a sql like join operation on two dicts, on the specified indexes
    """
    from collections import defaultdict

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# this is just a dirty hack to play an mp3 over a network, need netcat and mplayer
# on the sending machine (replace localhost with ip):
nc localhost 1234 < x.mp3
# on the playing machine:
nc -l -p 1234 | mplayer -

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# this will fill a disk to 5TB with one command, accounting for existing disk usage
# $a will be in kilobytes, so it must be converted in the expr to units of 150MB
# bs is set for efficiency, results on your disk may vary, if you change this, you'll need to change the number at the end in expr (currently 1024 * 150)
# the sed command specifies line 9 of the output pulled from df -k, you will need to change for your df output
dd if=/dev/zero of=/mnt/partition/bigfile bs=150MB count=$(let "a = 5368709120-`df -k | awk '{ print $3 "\t" }' | sed -n '9p'`"; expr $a / 153600)

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# this is a work in progress notepad, will include pdftk and ghostscript stuff

# replace page 13 of doc1.pdf with doc2.pdf
pdftk A=doc1.pdf B=doc2.pdf cat A1-12 B1 A14-end output out1.pdf

# remove the first 4 pages from in.pdf
pdftk A=in.pdf cat A5-end output out.pdf

# use ghostscript to combine PDFs
gs -dBATCH -dNOPAUSE -q -sDEVICE=pdfwrite -dAutoRotatePages=/None -sOutputFile=finished.pdf  file1.pdf file2.pdf file3.pdf

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#! /usr/bin/env python3
#
#  Σ i
# i=s

from functools import reduce

# the sequence to sum, you can use range(blah) as well
s = [1, 2, 3, 5]

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# truncate num_bytes off the end of a file
import os

def trunc(filename, num_bytes):
    with open(filename, 'rb+') as fi:
        fi.seek(-1 * num_bytes, os.SEEK_END)
        fi.truncate()

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sudo apt-get install calibre
ebook-convert book.epub book.mobi

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0.0.0.0   www.example.com
0.0.0.0   example.com
::0       www.example.com
::0       example.com