Python小试使用列表解析式简化代码

Posted 2020-12-20 Bioinfarmer

列表解析式的好处：

• 代码简洁
• 可读性强
• 运行快

示例

来自《Python编程》中的一个例子：同时投掷两颗面数不同的骰子（如一个6面的D6和一个10面的D10）n次，统计两个骰子点数之和，并用Pygal绘制bar图，进行交互可视化。

不用列表解析

from random import randint
import pygal

class Die():
    ‘‘‘表示一个骰子的类‘‘‘
    def __init__(self, num_sides=6):
        self.num_sides = num_sides

    def roll(self):
        return randint(1, self.num_sides)
    
die_1 = Die()
die_2 = Die(10)

results = []
for roll_num in range(50000):
    result = die_1.roll() + die_2.roll()
    results.append(result)

frequencies = []
max_result = die_1.num_sides + die_2.num_sides
for value in range(1, max_result+1):
    frequency = results.count(value)
    frequencies.append(frequency)

#可视化
hist = pygal.Bar()
hist.title = ‘Results of rolling a D6 and a D10 50000 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(‘D6 + D10‘,frequencies)
hist.render_to_file(‘different_dice_visual.svg‘)

对以上循环都改用列表解析

from random import randint
import pygal

‘‘‘省略Class Die‘‘‘

die_1 = Die()
die_2 = Die(10)

results = [die_1.roll()+die_2.roll() for i in range(50000)]
print(results)

max_result = die_1.num_sides + die_2.num_sides
frequencies = [results.count(x) for x in range(1, max_result)]
print(frequencies)

#可视化
hist = pygal.Bar()
hist.title = ‘Results of rolling a D6 and a D10 50000 times.‘
hist.x_labels = [str(x) for x in range(2,17)]
hist.x_title = "Result"
hist.y_title = "Frequency of Result"

hist.add(‘D6 + D10‘,frequencies)
hist.render_to_file(‘different_dice_visual.svg‘)

可视化结果