【Python编程：从入门到实践】第十五章：生成数据

15-1 立方：数字的三次方被称为其立方。请绘制一个图形，显示前5个整数的立方值，在绘制一个图形，显示前面5000个整数的立方值。

 前5个整数的立方值：

import matplotlib.pyplot as plt

x_values  = [1,2,3,4,5]
y_values = [1,8,27,64,125]
plt.title("Li Fang ")
plt.plot(x_values,y_values,linewidth = 5)
plt.xlabel("Value",fontsize = 14)
plt.ylabel("Square of Value",fontsize = 14)
plt.tick_params(axis = 'both' , labelsize = 14)
plt.show()

结果：

前面5000个整数的立方值：

import matplotlib.pyplot as plt

x_values  = list(range(1,50001))
y_values = [x**3 for x in x_values]
plt.title("Li Fang ")
plt.scatter(x_values,y_values,linewidth = 5,edgecolor = 'none')
plt.xlabel("Value",fontsize = 14)
plt.ylabel("Square of Value",fontsize = 14)
plt.tick_params(axis = 'both' , labelsize = 14)
plt.show()

结果：

15-2 彩色立方：给你前面的立方图指定颜色映射

import matplotlib.pyplot as plt

x_values  = [1,2,3,4,5]
y_values = [1,8,27,64,125]
plt.title("Li Fang ")
plt.plot(x_values,y_values,linewidth = 5,c = 'red')
plt.xlabel("Value",fontsize = 14)
plt.ylabel("Square of Value",fontsize = 14)
plt.tick_params(axis = 'both' , labelsize = 14)
plt.show()

结果：

15-3 分子运动：修改rw_visual.py，将其中的plt.scatter()替换为plt.plot()，为模拟花粉在水滴表面的运动路径，向plt.plot()传递rw.x_values和rw.y_values，并指定实参值linewidth。使用5000个点而不是50000个点。

rw_visual.py

import matplotlib.pyplot as plt

from random_walk import RandomWalk
rw = RandomWalk()
rw.fill_walk()
plt.plot(rw.x_values,rw.y_values,linewidth = 2)

plt.show()

random_walk.py

from random import choice
class RandomWalk(object):
	"""docstring for RandomWalk"""
	def __init__(self, num_points = 5000):
		self.num_points = num_points

		self.x_values = [0]
		self.y_values = [0]

	def fill_walk(self):
		while len(self.x_values) < self.num_points: 
			x_direction = choice([1,-1])
			x_distance = choice([0,1,2,3,4])
			x_step = x_direction * x_distance

			y_direction = choice([1,-1])
			y_distance = choice([0,1,2,3,4])
			y_step = y_direction * y_distance

			if x_step == 0  and y_step ==0:
				continue
			else:
				next_x = self.x_values[-1] + x_step
				next_y = self.y_values[-1] + y_step

				self.x_values.append(next_x)
				self.y_values.append(next_y)

结果：

15-4 改进的随机漫步：在类RandomWalk中，x_step 和 y_step 是根据相同的条件生成的：从列表【1，-1】中随机地选择方向，并经列表【0,1,2,3,4】中随机地选择距离。请修改这些列表中的值，看看对随机漫步路径有何影响。长沙使用更长距离选择列表，如0~8；或者将-1从x或y方向列表中删除

15-5 重构：方法fill_walk()很长。请新建一个名为get_step()的方法，用于确定每次漫步的距离和方向，并计算这次漫步将如何移动。然后，在fill_work() 中调用get_step()两次：

x_step = self.get_step()

y_step = self.get_step()

通过这样的重构，可缩小fill_walk() 的规模，让这个方法阅读和理解起来更容易

from random import choice class RandomWalk(object): """docstring for RandomWalk""" def __init__(self, num_points = 5000): self.num_points = num_points self.x_values = [0] self.y_values = [0] def fill_walk(self): while len(self.x_values)< self.num_points: x_step = self.get_step() y_step = self.get_step() if x_step == 0 and y_step ==0: continue else: next_x = self.x_values[-1] + x_step next_y = self.y_values[-1] + y_step self.x_values.add(next_x) self.y_values.add(next_y) def get_step(self): direction = choice([1,-1]) distance = choice([0,1,2,3,4]) step = direction * distance

return step

15-6 自动生成标签：请修改die.py 和 dice_visual.py，将用来设置 hist.x_labels 值的列表替换为字节自动生成这种列表的循环。如果你熟悉列表解析，可尝试将 die_visual.py 和 dice_visual.py 中的其他 for 循环也替换为列表解析。

die_visual.py

from die import Die
import pygal
def num2char(x):
	return str(x)
die1 = Die()
die2 = Die()
results = []

for roll_num in range(1000):
	result = die1.roll() + die2.roll()
	results.append(result)
# print(results)
frequencies = []
max_result = die1.num_sides + die2.num_sides
for value in range(1,max_result+1):
	frequency = results.count(value)
	frequencies.append(frequency)

hist = pygal.Bar()
hist.title = "Result of rolling me D6 1000 times."
hist.x_labels = list(map(num2char,list(range(1,max_result+1))))
print(hist.x_labels)
hist.x_title = "Result"
hist.y_title = "Frequency of Result"

hist.add('D6+D6',frequencies)
hist.render_to_file('dice1_visual.svg')

15-7 两个D8骰子：请模拟同时透支两个8面骰子1000次的结果。逐渐增加投掷骰子的次数，知道系统不堪重负为止。

die.py

from random import randint
class Die(object):
	"""docstring for Die"""
	def __init__(self, num_sides = 8):
		self.num_sides = num_sides

	def roll(self):
		return randint(1,self.num_sides)
		

die_visual.py

from die import Die
import pygal

die1 = Die()
die2 = Die()
results = []

for roll_num in range(1000):
	result = die1.roll() + die2.roll()
	results.append(result)
frequencies = []
max_result = die1.num_sides + die2.num_sides
for value in range(2,max_result+1):
	frequency = results.count(value)
	frequencies.append(frequency)

hist = pygal.Bar()
hist.title = "Result of rolling me D8 1000 times."
hist.x_labels = ['2','3','4','5','6','7','8','9','10','11','12','13','14','15','16']
hist.x_title = "Result"
hist.y_title = "Frequency of Result"

hist.add('D8+D8',frequencies)
hist.render_to_file('dice1_visual.svg')

结果：

15-8 同时投掷三个骰子：如果你同时掷三个D6骰子，可能得到的最小点数为3，而最大点数为18,。请通过可视化展示同时掷三个D6骰子的结果

die_visual.py

from die import Die
import pygal

die1 = Die()
die2 = Die()
die3 = Die()
results = []

for roll_num in range(1000):
	result = die1.roll() + die2.roll() +  die3.roll()
	results.append(result)
frequencies = []
max_result = die1.num_sides + die2.num_sides + die3.num_sides
for value in range(2,max_result+1):
	frequency = results.count(value)
	frequencies.append(frequency)

hist = pygal.Bar()
hist.title = "Result of rolling me D6 1000 times."
hist.x_labels = ['2','3','4','5','6','7','8','9','10','11','12','13','14','15','16','17','18']
hist.x_title = "Result"
hist.y_title = "Frequency of Result"

hist.add('D6+D6+D6',frequencies)
hist.render_to_file('dice1_visual.svg')

结果：

15-9 将点数相乘：同时掷两个骰子时，通常将它们的点数相加。通过可视化展示将两个骰子的点数相乘的结果

from die import Die
import pygal
def num2char(x):
	return str(x)
die1 = Die()
die2 = Die()
results = []

for roll_num in range(1000):
	result = die1.roll() * die2.roll()
	results.append(result)
# print(results)
frequencies = []
max_result = die1.num_sides * die2.num_sides
for value in range(1,max_result+1):
	frequency = results.count(value)
	frequencies.append(frequency)

hist = pygal.Bar()
hist.title = "Result of rolling me D6 1000 times."
hist.x_labels = list(map(num2char,list(range(1,max_result+1))))
print(hist.x_labels)
hist.x_title = "Result"
hist.y_title = "Frequency of Result"

hist.add('D6*D6',frequencies)
hist.render_to_file('dice1_visual.svg')

结果：

15-10 练习使用本章介绍的两个库：尝试使用 matplotlib 通过可视化来模拟值骰子的情况。
die_scatter.py

import matplotlib.pyplot as plt
from die import Die

die1 = Die()
die2 = Die()
results = []

for roll_num in range(1000):
	result = die1.roll() + die2.roll()
	results.append(result)
# print(results)
frequencies = []
max_result = die1.num_sides + die2.num_sides
for value in range(1,max_result+1):
	frequency = results.count(value)
	frequencies.append(frequency)
print(frequencies)
plt.plot(list(range(1,max_result+1)),frequencies,linewidth = 2)
plt.title("Result of rolling me D6 1000 times.")
plt.xlabel ("Result",fontsize = 14)
plt.ylabel("Square of D6 1000 times")
plt.show()

结果：

random_walk_Pygal.py