Question

__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"

在这个片段中，我想在函数search_student中使用一个变量参数选项，这样如果我传递roll_no，email，那么如果找到该id的学生，那么只有roll＆amp; amp ;电子邮件将与姓名一起打印。但如果我没有通过任何论证，那么只会打印名称

Answer 1

使用布尔值设置是否打印滚动和电子邮件的标志：

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')]

输出：

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'

我还会使用id作为密钥将用户存储在dict中：

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"

然后传递一个dict作为数据库：

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')}

输出相同：

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'

你可能最好使用dict来处理所有逻辑，但getattr可以使用** 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)

我们需要在用户输入无效的关键字/属性时捕获，有很多方法可以处理它，但一种简单的方法是捕获属性错误：

        try:
            print("Student {}: {}".format(k, getattr(get, k)))
        except AttributeError:
            print("Informative message or whatever is suitable")

或者如果返回False，请使用hasattr并执行任何操作：

 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)))

或者将默认值传递给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:....

Answer 2

您可以使用**表示法将可变数量的命名参数传递给您的函数。

如果参数为**args，那么它将是函数定义中尚未定义的任何命名参数的字典，然后您可以检查roll_no或email是否为出现在args中，如果是，请按照你的逻辑行事。

示例代码 -

>>> 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

Answer 3

所以这不是答案，而是一篇帖子，因为@Rob要求进一步澄清

所以如果函数存在，请说func(database=None, ID=None, [optionals])

所以当你致电func(DATABASE, 1, roll_no, email)时 ID为1＆amp;他/她的电子邮件和卷也将被打印

但如果我通过func(DATABASE, 1, roll_no, email, phone) 然后命名滚动电子邮件＆amp;将打印电话号码，但如果我只是给DATABASE＆amp; ID＆amp;没有选项，那么只应打印名称..如果没有找到该ID的记录，那么它不应该打印任何内容

如何在函数中传递namedtuple的可选参数

3 个答案: