base_model.py

#!/usr/bin/python3
"""This module defines a base class for all models in our hbnb clone"""
import uuid
from datetime import datetime
import sqlalchemy
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, String, DateTime
import os

if os.environ.get('HBNB_TYPE_STORAGE') == 'db':
    Base = sqlalchemy.orm.declarative_base()
else:
    Base = object


class BaseModel:
    """A base class for all hbnb models"""

    if os.environ.get('HBNB_TYPE_STORAGE') == 'db':
        id = Column(String(60), nullable=False, primary_key=True)
        created_at = Column(DateTime, nullable=False,
                            default=datetime.utcnow())
        updated_at = Column(DateTime, nullable=False,
                            default=datetime.utcnow())

    def __init__(self, *args, **kwargs):
        """Instatntiates a new model"""
        self.id = str(uuid.uuid4())
        self.created_at = datetime.now()
        self.updated_at = self.created_at

        if kwargs:
            for at in ['created_at', 'updated_at']:
                if at in kwargs.keys():
                    kwargs[at] = datetime.fromisoformat(kwargs[at])
            if '__class__' in kwargs.keys():
                del kwargs['__class__']
            self.__dict__.update(kwargs)

    def __str__(self):
        """Returns a string representation of the instance"""
        obj = self.__dict__.copy()
        try:
            del obj['_sa_instance_state']
        except KeyError:
            pass
        return '[{}] ({}) {}'.format(self.__class__.__name__,
                                     self.id, obj)

    def save(self):
        """Updates updated_at with current time when instance is changed"""
        from models import storage
        self.updated_at = datetime.now()
        storage.new(self)
        storage.save()

    def to_dict(self):
        """Convert instance into dict format"""
        dictionary = {}
        dictionary.update(self.__dict__)
        dictionary.update({'__class__':
                          (str(type(self)).split('.')[-1]).split('\'')[0]})
        dictionary['created_at'] = self.created_at.isoformat()
        dictionary['updated_at'] = self.updated_at.isoformat()
        try:
            del dictionary['_sa_instance_state']
        except KeyError:
            pass
        return dictionary

    def delete(self):
        """Delete the class instance"""
        from models import storage
        storage.delete(self)