How to pass an optional namedtuple parameter in a function
__author__ = 'mayukhsarkar'
import collections
def search_student(database=None, ID=None):
flag = False
try:
if ID is None or ID == 0:
raise TypeError
for each in database:
if each.id == ID:
print 'Student Name: ', each.name
flag = True
except TypeError:
print 'Provide the arguments properly'
finally:
return flag
studentDatabase = collections.namedtuple("student", "id name roll_no phone email")
DATABASE = [studentDatabase(1, 'Mayukh Sarkar', 9, '555-2312', 'mayukh2012@hotmail,com'),
studentDatabase(2, 'Alisha Sengupta', 7, '555-1345', 'alisha@gmail.com')]
if not search_student(DATABASE, 1):
print "Data not found"
In this snippet, I want an argument variable parameter in a function search_student
so that if I pass roll_no
, email
then if a student of that ID is found, only the roll and email will be printed along with the name. But if I pass no arguments, only the name is printed
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Use boolean values to set a flag for movie and email printing:
def search_student(database=None, ID=None, roll=False, email=False):
if ID is None or ID == 0:
print 'Provide the arguments properly'
return False
for each in database:
if each.id == ID:
print 'Student Name: {}'.format(each.name)
if roll:
print 'Stutent Roll: {}'.format(each.roll_no)
if email:
print("Student email: {}".format(each.email))
break
else:
return "User does not exist in database"
studentDatabase = collections.namedtuple("student", "id name roll_no phone email")
DATABASE = [studentDatabase(1, 'Mayukh Sarkar', 9, '555-2312', 'mayukh2012@hotmail,com'),
studentDatabase(2, 'Alisha Sengupta', 7, '555-1345', 'alisha@gmail.com')]
Output:
In [9]: search_student(DATABASE, 1, email=True,roll=True)
Student Name: Mayukh Sarkar
Stutent Roll: 9
Student email: mayukh2012@hotmail,com
In [10]: search_student(DATABASE, 1,roll=True)
Student Name: Mayukh Sarkar
Stutent Roll: 9
In [11]: search_student(DATABASE, 1, email=True)
Student Name: Mayukh Sarkar
Student email: mayukh2012@hotmail,com
In [12]: search_student(DATABASE, 1)
Student Name: Mayukh Sarkar
In [13]: search_student(DATABASE, 5)
Out[13]: 'User does not exist in database'
I would also store users in a dict using id as key:
def search_student(database=None, ID=None, roll=False, email=False):
if ID is None or ID == 0:
print 'Provide the arguments properly'
return False
get = database.get(ID)
if get is not None:
print 'Student Name: {}'.format(get.name)
if roll:
print 'Student Roll: {}'.format(get.roll_no)
if email:
print("Student email: {}".format(get.email))
else:
return "User does not exist in database"
Then pass the dict as a database:
studentDatabase = collections.namedtuple("student", "id name roll_no phone email")
DATABASE = {1: studentDatabase(1, 'Mayukh Sarkar', 9, '555-2312', 'mayukh2012@hotmail,com'),
2: studentDatabase(2, 'Alisha Sengupta', 7, '555-1345', 'alisha@gmail.com')}
The conclusion is the same:
In [18]: search_student(DATABASE, 1, email=True,roll=True)Student Name: Mayukh Sarkar
Student Roll: 9
Student email: mayukh2012@hotmail,com
In [19]: search_student(DATABASE, 1,roll=True)
Student Name: Mayukh Sarkar
Student Roll: 9
In [20]: search_student(DATABASE, 1, email=True)
Student Name: Mayukh Sarkar
Student email: mayukh2012@hotmail,com
In [21]: search_student(DATABASE, 1)
Student Name: Mayukh Sarkar
In [22]: search_student(DATABASE, 5)
Out[22]: 'User does not exist in database'
You might be better off using a dict for all your logic, but getattr will work with ** kwargs:
import collections
def search_student(database=None, ID=None, **kwargs):
if ID is None or ID == 0:
print 'Provide the arguments properly'
return False
get = database.get(ID)
if get is not None:
print 'Student Name: {}'.format(get.name)
for k in kwargs:
print("Student {}: {}".format(k, getattr(get,k)))
else:
return "User does not exist in database"
studentDatabase = collections.namedtuple("student", "id name roll_no phone email")
DATABASE = {1: studentDatabase(1, 'Mayukh Sarkar', 9, '555-2312', 'mayukh2012@hotmail,com'),
2: studentDatabase(2, 'Alisha Sengupta', 7, '555-1345', 'alisha@gmail.com')}
search_student(DATABASE,1,roll_no=True,email=True)
We need to catch when the user enters an invalid keyword / attribute, there are many ways to handle it, but an easy way is to catch the attribute error:
try:
print("Student {}: {}".format(k, getattr(get, k)))
except AttributeError:
print("Informative message or whatever is suitable")
Or use hasattr and do whatever you want if it returns False:
if get is not None:
print 'Student Name: {}'.format(get.name)
for k in kwargs:
if not hasattr(get,k):
continue
print("Student {}: {}".format(k, getattr(get, k)))
Or pass a default value to getattr:
if get is not None:
print 'Student Name: {}'.format(get.name)
for k in kwargs:
val = getattr(get, k,False)
if val:
print("Student {}: {}".format(k, val))
else:....
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You can use the notation **
to pass a variable number of named arguments to your function.
If an argument **args
then it will be a dictionary of any named arguments that are not yet defined in the function definition, then you can check if roll_no
or is present email
in args
, if so do your logic.
Examples of codes -
>>> def func(**args):
... print(args)
... if 'abc' in args:
... print(args['abc'])
...
>>> func(hello=10)
{'hello': 10}
>>> func(hello=10,abc="Student")
{'hello': 10, 'abc': 'Student'}
Student
>>> def search_student(database=None, ID=None, **args):
... if 'roll_no' in args:
... print(args['roll_no'])
...
>>> search_student(roll_no=10)
10
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so this is not an answer but a post because @Rob asked for more clarification
so if the function exists, say func(database=None, ID=None, [optionals])
so when you call the func(DATABASE, 1, roll_no, email)
name of the person whose id is 1 and his / her email and roll will also be printed
but if I go through func(DATABASE, 1, roll_no, email, phone)
it will print a letter with the roll number and phone number, but if I just give the database and ID and also no options then only the name should be printed. If no entry is found with this id, then it shouldn't print anything
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