result2
Swift style Result for Python
We can not use exceptions as logical judgments, for example:
class UserNotExistsException(Exception):
pass
class UserNotValidException(Exception):
pass
def get_valid_user_by_email(email):
"""
Return user instance
"""
user = get_user(email)
if user:
if user.valid is False:
raise UserNotValidException
return user
raise UserNotExistsException
try:
user = get_user_by_email('superpowerlee@gmail.com')
# do something if user exists ...
except UserNotExistsException, e:
# to create new user page with reason
except UserNotValidException, e:
# to create new user page with reasonthis code use try .. except as if, it's not a right way. So, you change the code, like next:
def get_valid_user_by_email(email):
"""
Return user instance
"""
user = get_user(email)
if user:
if user.valid is False:
return False, u"user not valid"
return True, user
return False, u"user not exists"
result, data = user = get_user_by_email('superpowerlee@gmail.com')
if result:
# do something if user exists ...
else:
# to create new user page with reason
In this case, what's the meaning of variable data ? The semantics in this code are ambiguous. It's easy to let us make mistake.
Use result2, your can rewrite the code above, use swift style result type, for example:
from result2 import Result, Ok, Err
def get_valid_user_by_email(email):
"""
Return user instance
"""
user = get_user(email)
if user:
if user.valid is False:
return Err("user not valid")
return Ok(user)
return Err("user not exists")
result = get_user_by_email('superpowerlee@gmail.com')
if result == Result.Ok:
# do something if user exists ...
else:
# to create new user page with reasonThis one will be better, with clear logic and semantics.
That's why i write this lib. Thers is a similar lib https://github.com/dbrgn/result, why write new one? Because this one can return multi value.
Useage
Install:
pip install result2
When you return something:
return Ok(data) # return one value
return Ok(data1, data2, data3 ...) # return a lot of value
return Err(reson) # return failureTo check if return right:
if result == Result.Ok:To check if return not right:
if result == Result.Err:To get return value:
user = result() # when return one value
v1, v2, v3 = result() # when return multi value
error = result() # get error reasonThat's all of it, enjoy.
