python教程命名元组示例分析

from collections import namedtuple
Subscriber = namedtuble('Subscriber', ['addr', 'joined'])
sub = Subscriber('jonesy@example.com', '2012-10-19')
print(sub)
# Subscriber(addr='jonesy@example.com', joined='2012-10-19') 
print(sub.addr)
# 'jonesy@example.com'
print(sub.joined)
# '2012-10-19'

print(len(sub))
# 2
addr, joined = sub
print(addr)
# 'jonesy@example.com' 
print(joined)
# '2012-10-19'

from collections import namedtuple
 
Stock = namedtuple('Stock', ['name', 'shares', 'price'])
def compute_cost(records):
    total = 0.0
    for rec in records:
        s = Stock(*rec)
        total += s.shares * s.price
        # 若此处为 total += s[1] * s.[2] 则数据一变，代码也不对
    return total

s = Stock('ACEM', 100, 123.45)
print(s)
# Stock(name='ACME', share=100, price=123.45)
s.share = 75
# Traceback (most recent call last):
# File "<stdin>", line 1, in <module>
# AttributeError: can't set attribute

s = s._replace(share=75)
print(s)
# Stock(name='ACME', share=75, price=123.45)

from collection import namedtuple
Stock = namedtuple('Stock', ['name', 'share', 'price', 'data', 'time'])
# Create a prototype instance
stock_prototype = Stock('', 0, 0.0, None, NOne) 
# Function to convert a dictionary to a Stock
def dict_to_stock(s):
    return stock_prototype.replace(**s)

>>> a = {'name': 'ACME', 'shares': 100, 'price': 123.45}
>>> dict_to_stock(a)
Stock(name='ACME', shares=100, price=123.45, date=None, time=None)
>>> b = {'name': 'ACME', 'shares': 100, 'price': 123.45, 'date': '12/17/2012'}
>>> dict_to_stock(b)
Stock(name='ACME', shares=100, price=123.45, date='12/17/2012', time=None)