Firebase push algorithm in Python (ref: https://www.firebase.com/blog/2015-02-11-firebase-unique-identifiers.html)

firebase_pushid.py

import random
import time
import numpy
from exceptions import ValueError


class PushID(object):
    # Modeled after base64 web-safe chars, but ordered by ASCII.
    PUSH_CHARS = ('-0123456789'
                  'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
                  '_abcdefghijklmnopqrstuvwxyz')

    def __init__(self):

        # Timestamp of last push, used to prevent local collisions if you
        # pushtwice in one ms.
        self.lastPushTime = 0

        # We generate 72-bits of randomness which get turned into 12
        # characters and appended to the timestamp to prevent
        # collisions with other clients.  We store the last characters
        # we generated because in the event of a collision, we'll use
        # those same characters except "incremented" by one.
        self.lastRandChars = numpy.empty(12, dtype=int)

    def next_id(self):
        now = int(time.time() * 1000)
        duplicateTime = (now == self.lastPushTime)
        self.lastPushTime = now
        timeStampChars = numpy.empty(8, dtype=str)

        for i in range(7, -1, -1):
            timeStampChars[i] = self.PUSH_CHARS[now % 64]
            now = int(now / 64)

        if (now != 0):
            raise ValueError('We should have converted the entire timestamp.')

        uid = ''.join(timeStampChars)

        if not duplicateTime:
            for i in range(12):
                self.lastRandChars[i] = int(random.random() * 64)
        else:
            # If the timestamp hasn't changed since last push, use the
            # same random number, except incremented by 1.
            for i in range(11, -1, -1):
                if self.lastRandChars[i] == 63:
                    self.lastRandChars[i] = 0
                else:
                    break
            self.lastRandChars[i] += 1

        for i in range(12):
            uid += self.PUSH_CHARS[self.lastRandChars[i]]

        if len(uid) != 20:
            raise ValueError('Length should be 20.')
        return uid

Great job on the python port @risent! Why is the else here necessary though?

Edit: Figured it out. Again, thanks for this!

thank you very much...i was in confusion.

thank you for the python script @risent. I am very new to python and I can't seem to call the PushID class correctly.

I am trying to generate a UID for each row in 'full_results_date.csv' and re-write the rows to a new csv 'results_uid.csv' with the uid of each row appended in the new column.

I have added the following code below your script.

`with open('full_results_date.csv', 'r') as csvinput:
with open('results_uid.csv', 'w') as csvoutput:
writer = csv.writer(csvoutput, lineterminator='\n')
reader = csv.reader(csvinput)

    all = []
    row = next(reader)
    row.append(PushID())
    all.append(row)

    for row in reader:
        row.append(PushID())
        all.append(row)

    writer.writerows(all)`

the 'results_uid.csv' has a column appended but each cell in the column is not a UID. Instead, the object location is being returned -
<main.PushID object at 0x109727518>

Thanks man. It was very helpful

import firebase_pushid

print(firebase_pushid.PushID().next_id())

had to remove line 4 to have it work on python 3.8.10