Profiling Your Python Code

Ngalim Siregar — Wed, 05 Jan 2022 04:34:59 +0000

Sometimes you want to profile just a single function in your Python program. To profile single function on Python program, we can use cProfile to profile single function

def create_array():
  arr=[]
  for i in range(0,400000):
    arr.append(i)

def print_statement():
  print('Array created successfully')


def main():
  create_array()
  print_statement()

if __name__ == '__main__':
    import cProfile, pstats
    profiler = cProfile.Profile()
    profiler.enable()
    main()
    profiler.disable()
    stats = pstats.Stats(profiler).sort_stats('ncalls')
    stats.print_stats()

That will profile method create_array and print_statement. By using pprofiler library we can simplify those step to single decorator call

from pprofiler import pprof

...

@pprof()
def main():
  create_array()
  print_statement()

if __name__ == '__main__':
    main()

By default pprofiler will sort by ncalls, we can use other sorting key by define it.

from pprofiler import pprof

...

@pprof(sort_by='time')
def main():
  create_array()
  print_statement()

if __name__ == '__main__':
    main()

SQLAlchemy Events

Ngalim Siregar — Tue, 17 Aug 2021 08:07:17 +0000

During the normal operation in SQLAlchemy ORM objects may be created, updated, and destroyed. SQLAlchemy provides hooks into this object life cycle so that you can control your application and its data.

These callbacks allow you to trigger logic before or after an alteration of an object's state.

Here is a sample of Flask-SQLAlchemy Model

class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(80), unique=True, nullable=False)

    def __repr__(self):
        return '<User %r>' % self.username

If we want to add callback to lowercase username before save, we can use sqlalchemy.event.listens_for

from sqlalchemy import event


class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(80), unique=True, nullable=False)

    def __repr__(self):
        return '<User %r>' % self.username


@event.listens_for(User, "before_insert")
def lowercase(mapper, connection, target):
    target.username = target.username.lower()

By using sqlalchemy-events library, we can simplify those event listen to

from sqlalchemy_events import listen_events, on


@listen_events
class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(80), unique=True, nullable=False)

    @on("before_insert")
    def lowercase_username(mapper, conn, self):
        self.username = self.username.lower()

    def __repr__(self):
        return '<User %r>' % self.username

DEV Community: Ngalim Siregar

Profiling Your Python Code

SQLAlchemy Events