mirror of
https://github.com/apachecn/ailearning.git
synced 2026-04-23 18:13:05 +08:00
560 lines
26 KiB
Markdown
560 lines
26 KiB
Markdown
# super() 函数
|
||
|
||
```py
|
||
super(CurrentClassName, instance)
|
||
```
|
||
|
||
返回该类实例对应的父类对象。
|
||
|
||
In [1]:
|
||
|
||
```py
|
||
class Leaf(object):
|
||
def __init__(self, color="green"):
|
||
self.color = color
|
||
def fall(self):
|
||
print "Splat!"
|
||
|
||
class MapleLeaf(Leaf):
|
||
def change_color(self):
|
||
if self.color == "green":
|
||
self.color = "red"
|
||
def fall(self):
|
||
self.change_color()
|
||
super(MapleLeaf, self).fall()
|
||
|
||
```
|
||
|
||
这里，我们先改变树叶的颜色，然后再找到这个实例对应的父类，并调用父类的 `fall()` 方法：
|
||
|
||
In [2]:
|
||
|
||
```py
|
||
mleaf = MapleLeaf()
|
||
|
||
print mleaf.color
|
||
mleaf.fall()
|
||
print mleaf.color
|
||
|
||
```
|
||
|
||
```py
|
||
green
|
||
Splat!
|
||
red
|
||
|
||
```
|
||
|
||
回到我们的森林例子，这里我们将森林 `Forest` 作为父类，并定义一个子类 `BurnableForest`：
|
||
|
||
In [3]:
|
||
|
||
```py
|
||
import numpy as np
|
||
|
||
class Forest(object):
|
||
""" Forest can grow trees which eventually die."""
|
||
def __init__(self, size=(150,150), p_sapling=0.0025):
|
||
self.size = size
|
||
self.trees = np.zeros(self.size, dtype=bool)
|
||
self.p_sapling = p_sapling
|
||
|
||
def __repr__(self):
|
||
my_repr = "{}(size={})".format(self.__class__.__name__, self.size)
|
||
return my_repr
|
||
|
||
def __str__(self):
|
||
return self.__class__.__name__
|
||
|
||
@property
|
||
def num_cells(self):
|
||
"""Number of cells available for growing trees"""
|
||
return np.prod(self.size)
|
||
|
||
@property
|
||
def tree_fraction(self):
|
||
"""
|
||
Fraction of trees
|
||
"""
|
||
num_trees = self.trees.sum()
|
||
return float(num_trees) / self.num_cells
|
||
|
||
def _rand_bool(self, p):
|
||
"""
|
||
Random boolean distributed according to p, less than p will be True
|
||
"""
|
||
return np.random.uniform(size=self.trees.shape) < p
|
||
|
||
def grow_trees(self):
|
||
"""
|
||
Growing trees.
|
||
"""
|
||
growth_sites = self._rand_bool(self.p_sapling)
|
||
self.trees[growth_sites] = True
|
||
|
||
def advance_one_step(self):
|
||
"""
|
||
Advance one step
|
||
"""
|
||
self.grow_trees()
|
||
|
||
```
|
||
|
||
* 将与燃烧相关的属性都被转移到了子类中去。
|
||
* 修改两类的构造方法，将闪电概率放到子类的构造方法上，同时在子类的构造方法中，用 `super` 调用父类的构造方法。
|
||
* 修改 `advance_one_step()`，父类中只进行生长，在子类中用 `super` 调用父类的 `advance_one_step()` 方法，并添加燃烧的部分。
|
||
|
||
In [4]:
|
||
|
||
```py
|
||
class BurnableForest(Forest):
|
||
"""
|
||
Burnable forest support fires
|
||
"""
|
||
def __init__(self, p_lightning=5.0e-6, **kwargs):
|
||
super(BurnableForest, self).__init__(**kwargs)
|
||
self.p_lightning = p_lightning
|
||
self.fires = np.zeros((self.size), dtype=bool)
|
||
|
||
def advance_one_step(self):
|
||
"""
|
||
Advance one step
|
||
"""
|
||
super(BurnableForest, self).advance_one_step()
|
||
self.start_fires()
|
||
self.burn_trees()
|
||
|
||
@property
|
||
def fire_fraction(self):
|
||
"""
|
||
Fraction of fires
|
||
"""
|
||
num_fires = self.fires.sum()
|
||
return float(num_fires) / self.num_cells
|
||
|
||
def start_fires(self):
|
||
"""
|
||
Start of fire.
|
||
"""
|
||
lightning_strikes = (self._rand_bool(self.p_lightning) &
|
||
self.trees)
|
||
self.fires[lightning_strikes] = True
|
||
|
||
def burn_trees(self):
|
||
"""
|
||
Burn trees.
|
||
"""
|
||
fires = np.zeros((self.size[0] + 2, self.size[1] + 2), dtype=bool)
|
||
fires[1:-1, 1:-1] = self.fires
|
||
north = fires[:-2, 1:-1]
|
||
south = fires[2:, 1:-1]
|
||
east = fires[1:-1, :-2]
|
||
west = fires[1:-1, 2:]
|
||
new_fires = (north | south | east | west) & self.trees
|
||
self.trees[self.fires] = False
|
||
self.fires = new_fires
|
||
|
||
```
|
||
|
||
测试父类：
|
||
|
||
In [5]:
|
||
|
||
```py
|
||
forest = Forest()
|
||
|
||
forest.grow_trees()
|
||
|
||
print forest.tree_fraction
|
||
|
||
```
|
||
|
||
```py
|
||
0.00284444444444
|
||
|
||
```
|
||
|
||
测试子类：
|
||
|
||
In [6]:
|
||
|
||
```py
|
||
burnable_forest = BurnableForest()
|
||
|
||
```
|
||
|
||
调用自己和父类的方法：
|
||
|
||
In [7]:
|
||
|
||
```py
|
||
burnable_forest.grow_trees()
|
||
burnable_forest.start_fires()
|
||
burnable_forest.burn_trees()
|
||
print burnable_forest.tree_fraction
|
||
|
||
```
|
||
|
||
```py
|
||
0.00235555555556
|
||
|
||
```
|
||
|
||
查看变化：
|
||
|
||
In [8]:
|
||
|
||
```py
|
||
import matplotlib.pyplot as plt
|
||
|
||
%matplotlib inline
|
||
|
||
forest = Forest()
|
||
forest2 = BurnableForest()
|
||
|
||
tree_fractions = []
|
||
|
||
for i in range(2500):
|
||
forest.advance_one_step()
|
||
forest2.advance_one_step()
|
||
tree_fractions.append((forest.tree_fraction, forest2.tree_fraction))
|
||
|
||
plt.plot(tree_fractions)
|
||
|
||
plt.show()
|
||
|
||
```
|
||
|
||
|
||
|
||
`__str__` 和 `__repr__` 中 `self.__class__` 会根据类型不同而不同：
|
||
|
||
In [9]:
|
||
|
||
```py
|
||
forest
|
||
|
||
```
|
||
|
||
Out[9]:
|
||
|
||
```py
|
||
Forest(size=(150, 150))
|
||
```
|
||
|
||
In [10]:
|
||
|
||
```py
|
||
forest2
|
||
|
||
```
|
||
|
||
Out[10]:
|
||
|
||
```py
|
||
BurnableForest(size=(150, 150))
|
||
```
|
||
|
||
In [11]:
|
||
|
||
```py
|
||
print forest
|
||
|
||
```
|
||
|
||
```py
|
||
Forest
|
||
|
||
```
|
||
|
||
In [12]:
|
||
|
||
```py
|
||
print forest2
|
||
|
||
```
|
||
|
||
```py
|
||
BurnableForest
|
||
|
||
``` |