Python：在for循环中添加到列表列表中答案

【问题标题】：Python: adding to list of lists both out and in a for loopPython：在for循环中添加到列表列表中
【发布时间】：2020-03-23 05:14:11
【问题描述】：

我想在 for 循环外创建一个索引值为 0 的新列表，然后使用 for 循环添加到同一个列表中。我的玩具例子是：

import random

data = ['t1', 't2', 't3']

masterlist = [['col1', 'animal1', 'animal2', 'animal3']]
animals = ['cat', 'dog', 'chinchilla']

for item in data:
    masterlist.append([item])
    for animal in animals:
        number1 = random.randint(1, 100)
        number2 = random.randint(1, 100)
        masterlist.append([str(number1) + ',' + str(number2)])

masterlist

但是这个输出：

[['col1', 'animal1', 'animal2', 'animal3'],
 ['t1'],
 ['52,69'],
 ['8,77'],
 ['75,66'],
 ['t2'],
 ['67,33'],
 ['85,60'],
 ['98,12'],
 ['t3'],
 ['60,34'],
 ['25,27'],
 ['100,25']]

我想要的输出是：

[['col1', 'animal1', 'animal2', 'animal3'],
 ['t1', '52,69', '8,77', '75,66'], 
 ['t2', '67,33', '85,60', '98,12'],
 ['t3', '60,34', '25,27', '100,25']]

【问题讨论】：

标签： python list for-loop random nested-lists

【解决方案1】：

您还可以按如下方式使用列表推导：

import random

data = ['t1', 't2', 't3']

masterlist = [['col1', 'animal1', 'animal2', 'animal3']]
animals = ['cat', 'dog', 'chinchilla']

for d in data:
     rv = [d] + [str(random.randint(1, 100)) + ',' + str(random.randint(1, 100)) for a in animals]

masterlist.append(rv)

或者在单个列表理解中更加核心：

masterlist+= [[d] + [str(random.randint(1, 100)) + ',' + str(random.randint(1, 100)) for a in animals] for d in data]

【讨论】：

【解决方案2】：

这个稍微重构你的代码的解决方案怎么样？

解决方案 1

import random

data = ['t1', 't2', 't3']

masterlist = [['col1', 'animal1', 'animal2', 'animal3']]
animals = ['cat', 'dog', 'chinchilla']

for item in data:
    rv = []
    rv.append(item)
    for animal in animals:
        number1 = random.randint(1, 100)
        number2 = random.randint(1, 100)
        rv.append(str(number1) + ',' + str(number2))
    masterlist.append(rv)

输出：

>>> masterlist
[['col1', 'animal1', 'animal2', 'animal3'],
 ['t1', '88,43', '85,62', '84,21'],
 ['t2', '44,99', '32,54', '83,50'],
 ['t3', '82,87', '90,83', '91,84']]

或者，以下将给出相同的结果。

解决方案 2

import random

data = ['t1', 't2', 't3']

masterlist = [['col1', 'animal1', 'animal2', 'animal3']]
animals = ['cat', 'dog', 'chinchilla']

for item in data:
    masterlist.append([item] + [f"{random.randint(1, 100)},{random.randint(1, 100)}" for animal in animals])

【讨论】：

【解决方案3】：

你可以做这样的事情。使用temp 列表来存储每次迭代的项目。此外，您在追加时使用了许多方括号，这导致列表过于嵌套。

import random

data = ['t1', 't2', 't3']

masterlist = [['col1', 'animal1', 'animal2', 'animal3']]
animals = ['cat', 'dog', 'chinchilla']

for item in data:
    temp = []
    temp.append(item)
    for animal in animals:
        number1 = random.randint(1, 100)
        number2 = random.randint(1, 100)
        temp.append(str(number1) + ',' + str(number2))
    masterlist.append(temp)

print(masterlist)

【讨论】：