from collections import namedtuple
 
# 基本例子
Point = namedtuple('Point',['x','y']) # 類名為Point,屬性有'x'和'y'
 
p = Point(11, y=22) # 用位置或關(guān)鍵字參數(shù)實例化，因為'x'在'y'前，所以x=11,和函數(shù)參數(shù)賦值一樣的
print(p[0]+p[1]) # 我們也可以使用下標來訪問
# 33
 
x, y = p # 也可以像一個元組那樣解析
print(x,y)
# (11, 22)
 
print(p.x+p.y) # 也可以通過屬性名來訪問
# 33
 
print(p) # 通過內(nèi)置的__repr__函數(shù)，顯示該對象的信息
# Point(x=11, y=22)

t = [11, 22] # 列表 list
p = Point._make(t) # 從列表中直接賦值，返回對象
print(Point(x=11, y=22))
# Point(x=11, y=22)

p = Point(x=11, y=22) # 新建一個對象
d = p._asdict() # 解析并返回一個字典對象
print(d)
# {'x': 11, 'y': 22}

p = Point(x=11, y=22) # x=11,y=22
print(p)
# Point(x=11, y=22)
 
d = p._replace(x=33) # x=33,y=22 新的對象
print(p)
# Point(x=11, y=22)
print(d)
# Point(x=33, y=22)

print(p._fields) # 查看屬性名
# ('x', 'y')
 
Color = namedtuple('Color', 'red green blue')
Pixel = namedtuple('Pixel', Point._fields + Color._fields) # 新建一個子類，使用多個屬性名
q = Pixel(11, 22, 128, 255, 0)
print(q)

Account = namedtuple('Account', ['type', 'balance'], defaults=[0])
print(Account._field_defaults)
#{'balance': 0}
print(Account('premium'))
#Account(type='premium', balance=0)

print(getattr(p, 'x'))
# 11

d = {'x': 11, 'y': 22} # 字典
p = Point(**d) # 雙星號是重點
print(p)
# Point(x=11, y=22)

EmployeeRecord = namedtuple('EmployeeRecord', 'name, age, title, department, paygrade')
 
import csv
for emp in map(EmployeeRecord._make, csv.reader(open("employees.csv", "r"))):
 # 這里每行返回一個對象 注意！
 print(emp.name, emp.title)
 
import sqlite3
conn = sqlite3.connect('/companydata') # 連接數(shù)據(jù)庫
cursor = conn.cursor()
cursor.execute('SELECT name, age, title, department, paygrade FROM employees')
for emp in map(EmployeeRecord._make, cursor.fetchall()):
 # 每行返回一個對象 注意！
 print(emp.name, emp.title)

NODES = "nodes"
EDGES = "edges"
RECEIVERS = "receivers"
SENDERS = "senders"
GLOBALS = "globals"
N_NODE = "n_node"
N_EDGE = "n_edge"
 
GRAPH_DATA_FIELDS = (NODES, EDGES, RECEIVERS, SENDERS, GLOBALS)
GRAPH_NUMBER_FIELDS = (N_NODE, N_EDGE)
 
class GraphsTuple(
	# 定義元組子類名 以及字典形式的鍵名（屬性名）
 collections.namedtuple("GraphsTuple",
    GRAPH_DATA_FIELDS + GRAPH_NUMBER_FIELDS)): 
 
	# 這個函數(shù)用來判斷依賴是否滿足，和我們的namedtuple關(guān)系不大
	def _validate_none_fields(self):
		"""Asserts that the set of `None` fields in the instance is valid."""
		if self.n_node is None:
		 raise ValueError("Field `n_node` cannot be None")
		if self.n_edge is None:
		 raise ValueError("Field `n_edge` cannot be None")
		if self.receivers is None and self.senders is not None:
		 raise ValueError(
			 "Field `senders` must be None as field `receivers` is None")
		if self.senders is None and self.receivers is not None:
		 raise ValueError(
			 "Field `receivers` must be None as field `senders` is None")
		if self.receivers is None and self.edges is not None:
		 raise ValueError(
			 "Field `edges` must be None as field `receivers` and `senders` are "
			 "None")
 
	# 用來初始化一些參數(shù) 不是重點
	def __init__(self, *args, **kwargs):
		del args, kwargs
		# The fields of a `namedtuple` are filled in the `__new__` method.
		# `__init__` does not accept parameters.
		super(GraphsTuple, self).__init__()
		self._validate_none_fields()
 
	# 這就用到了_replace()函數(shù),注意只要修改了屬性值
	# 那么就返回一個新的對象
	def replace(self, **kwargs):
		output = self._replace(**kwargs) # 返回一個新的實例 
		output._validate_none_fields() # pylint: disable=protected-access 驗證返回的新實例是否滿足要求
		return output
 
	# 這是為了針對tensorflow1版本的函數(shù)
	# 返回一個擁有相同屬性的對象，但是它的屬性值是輸入的大小和類型
	def map(self, field_fn, fields=GRAPH_FEATURE_FIELDS): # 對每個鍵應(yīng)用函數(shù)
	"""Applies `field_fn` to the fields `fields` of the instance.
	`field_fn` is applied exactly once per field in `fields`. The result must
	satisfy the `GraphsTuple` requirement w.r.t. `None` fields, i.e. the
	`SENDERS` cannot be `None` if the `EDGES` or `RECEIVERS` are not `None`,
	etc.
	Args:
	 field_fn: A callable that take a single argument.
	 fields: (iterable of `str`). An iterable of the fields to apply
		`field_fn` to.
	Returns:
	 A copy of the instance, with the fields in `fields` replaced by the result
	 of applying `field_fn` to them.
	"""
	return self.replace(**{k: field_fn(getattr(self, k)) for k in fields}) # getattr(self, k) 獲取的是鍵值對中的值, k表示鍵