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@jrivero
jrivero / csv_splitter.py
Created July 15, 2011 20:33 — forked from palewire/csv_splitter.py
A Python CSV splitter
import os
def split(filehandler, delimiter=',', row_limit=10000,
output_name_template='output_%s.csv', output_path='.', keep_headers=True):
"""
Splits a CSV file into multiple pieces.
A quick bastardization of the Python CSV library.
Arguments:
@jboner
jboner / latency.txt
Last active July 19, 2024 09:51
Latency Numbers Every Programmer Should Know
Latency Comparison Numbers (~2012)
----------------------------------
L1 cache reference 0.5 ns
Branch mispredict 5 ns
L2 cache reference 7 ns 14x L1 cache
Mutex lock/unlock 25 ns
Main memory reference 100 ns 20x L2 cache, 200x L1 cache
Compress 1K bytes with Zippy 3,000 ns 3 us
Send 1K bytes over 1 Gbps network 10,000 ns 10 us
Read 4K randomly from SSD* 150,000 ns 150 us ~1GB/sec SSD
@anantn
anantn / firebase_detect_data.js
Created December 18, 2012 00:54
Firebase: Detecting if data exists. This snippet detects if a user ID is already taken
function go() {
var userId = prompt('Username?', 'Guest');
checkIfUserExists(userId);
}
var USERS_LOCATION = 'https://SampleChat.firebaseIO-demo.com/users';
function userExistsCallback(userId, exists) {
if (exists) {
alert('user ' + userId + ' exists!');
@luke
luke / bulkupsert.py
Last active March 17, 2023 19:30
I needed to upsert (insert or update) bajillions of records into postgresql. After trying various libs including upsert (which was slow as hell) I ended up doing a bit of research and trying 3 different methods. This one won. While I'm manually building the sql string no user data is passed in. Its loaded via the copy from statement as CSV. Call…
import logging
import cStringIO
import csv
DEBUG = False
def data2csv(data):
si = cStringIO.StringIO()
cw = csv.writer(si, delimiter='\t',lineterminator="\n")
for row in data:
@karpathy
karpathy / min-char-rnn.py
Last active July 18, 2024 15:59
Minimal character-level language model with a Vanilla Recurrent Neural Network, in Python/numpy
"""
Minimal character-level Vanilla RNN model. Written by Andrej Karpathy (@karpathy)
BSD License
"""
import numpy as np
# data I/O
data = open('input.txt', 'r').read() # should be simple plain text file
chars = list(set(data))
data_size, vocab_size = len(data), len(chars)
@kelvintaywl
kelvintaywl / split.py
Last active May 9, 2024 11:39
Python Script to split CSV files into smaller files based on number of lines
import csv
import sys
import os
# example usage: python split.py example.csv 200
# above command would split the `example.csv` into smaller CSV files of 200 rows each (with header included)
# if example.csv has 401 rows for instance, this creates 3 files in same directory:
# - `example_1.csv` (row 1 - 200)
# - `example_2.csv` (row 201 - 400)
# - `example_3.csv` (row 401)
@valyala
valyala / README.md
Last active June 3, 2024 17:00
Optimizing postgresql table for more than 100K inserts per second

Optimizing postgresql table for more than 100K inserts per second

  • Create UNLOGGED table. This reduces the amount of data written to persistent storage by up to 2x.
  • Set WITH (autovacuum_enabled=false) on the table. This saves CPU time and IO bandwidth on useless vacuuming of the table (since we never DELETE or UPDATE the table).
  • Insert rows with COPY FROM STDIN. This is the fastest possible approach to insert rows into table.
  • Minimize the number of indexes in the table, since they slow down inserts. Usually an index on time timestamp with time zone is enough.
  • Add synchronous_commit = off to postgresql.conf.
  • Use table inheritance for fast removal of old data:
@tomysmile
tomysmile / mac-setup-redis.md
Last active July 16, 2024 04:45
Brew install Redis on Mac

type below:

brew update
brew install redis

To have launchd start redis now and restart at login:

brew services start redis
@navicore
navicore / sha256.scala.md
Last active September 15, 2022 13:58
sha256 single line function in scala

def sha256Hash(text: String) : String = java.security.MessageDigest.getInstance("SHA-256").digest(text.getBytes()).map(0xFF & ).map { "%02x".format() }.foldLeft(""){_ + _}

def sha256Hash(text: String) : String = String.format("%064x", new java.math.BigInteger(1, java.security.MessageDigest.getInstance("SHA-256").digest(text.getBytes("UTF-8"))))

verify via:

scala> sha256Hash("Rusty is a cowboy!")