Lets start with a very basic example which demonstrates why we might need functools.partial in the first place, then we will look into a more concrete example.
we have a power function which is used to compute powers obviously ;)
def power(base, exponent):
return base ** power
>>> power(2,3)
8
>>> power(3,3)
27Now suppose we want to introduce some custome functions which make use of power function
def square(base):
return power(base,2)
def cube(base):
return power(base,3)
# and lots more similar function definationsIn all the above cases we can see that the new function is generated by utillising the older funciton by just pre-determining one argument. in case of square() 2 is fixed while in case of cube() 3 is fixed.
Can we can do something better to achieve the same functionality as above? Yes!
lets see how.
def power(base, exponent):
return base ** power
square = functools.partial(power, exp=2)
cube = functools.partial(power,exp=3)
>>> print square(5)
25
>>> print cube(1)
1using functools.partial we were able to create new functions from existing one! :)
another example refrence
def _send_email(to, subject, body):
send_mail(
subject,
body,
settings.EMAIL_HOST_USER,
)
email_admin = partial(_send_email, to="admin@example.com")
email_general_it = partial(_send_email, to="it@example.com")
email_marketing = partial(_send_email, to="marketing@example.com")
email_sales = partial(_send_email, to="sales@example.com")
...
if thing_is_broken():
# the 'to' field is already filled in! Hooray!
email_admin(subject="It's brokened!", body='Fix it!')
if sales_people():
email_sales(subject="sales stuff", body="business, business, business!")