Counter¶

Installation¶

pip install litecounter

IMPORTANT: This module uses SQLite's UPSERT statement, so it needs to run at least with SQLite version 3.24.0 (released 2018-06-04).

If you need to run the latest version, with Python you can use pysqlite3 and override sqlite3

import pysqlite3 # pre-built if you install pysqlite3-binary
import sys
sys.modules['sqlite3'] = pysqlite3

In near releases you will be able to use a Connection instead of a just the database name to create the counter, so you won't need to override sqlite3 globally.

Use cases¶

You can use this to implement a persistent counter. It also uses some SQLite syntax to initialize keys to 0 when the counter starts on them, just as if you had a collections.defaultdict where the default is 0.

Examples¶

Set up 2 example key names and initialize the database.

TEST_1 = "key_test_1"
TEST_2 = "key_test_2"

from litecounter import SQLCounter

counter = SQLCounter(":memory:")

Increment or decrement a key¶

Now we can increment from 0 to 20 using the counter.incr(keyname) method. By default, when a key does not exist, it's set to 0.

for _ in range(20):
    counter.incr(TEST_1)

To check the current count of a key, use the method counter.count(keyname).

assert counter.count(TEST_1) == 20

Or decrement by 10 (from 20 to 10) using the counter.decr(keyname) method.

for _ in range(10):
    counter.decr(TEST_1)
    
assert counter.count(TEST_1) == 10

More examples.

# From 0 to -10, then -20.

for _ in range(10):
    counter.decr(TEST_2)
    
assert counter.count(TEST_2) == -10

for _ in range(10):
    counter.decr(TEST_2)
    
assert counter.count(TEST_2) == -20

We can set a key to 0 with the counter.zero(keyname) method.

counter.zero(TEST_1)

assert counter.count(TEST_1) == 0

# Increment the second test key by 100, from -20 to 80.

for _ in range(100):
    counter.incr(TEST_2)
    
assert counter.count(TEST_2) == 80

assert counter.count(TEST_1) == 0

Deleting a key¶

Use the counter.delete(keyname) method.

counter.delete(TEST_1)

assert counter.count(TEST_1) is None

When the key does not exist, .delete() just ignores it

counter.delete("foobar")

# Nothing happens

Printing¶

The counter implements a __repr__ method, so you can use print() on it.

import random

for key in ["foo", "bar", "baz", "foobar", "asd", TEST_1]:
    for _ in range(random.randint(0,10)):
        counter.incr(key)

print(counter)

# SQLCounter(Connection='sqlite3.Connection(...)', items=[('key_test_2', 80), ('foo', 8), ('baz', 5), ('foobar', 6), ('key_test_1', 10)])