使用for循环将元素导入列表

Question

我对Python比较陌生，我试图在列表new_bandit_probs中添加一个随机数(new_bandit)，如果I == x。但是如果我打印new_bandit_probs列表，我只是得到一个空列表。有人能帮我一下吗?

import numpy as np
bandit_probs = [0.1, 0.4, 0.9] 
N_bandits = len(bandit_probs)
N_experiments = 1 
N_episodes = 100 
new_bandit = np.random.random ()
x = np.random.randint(0, N_episodes)
new_bandit_probs = []
def update_bandit_probs (bandit_probs, N_episodes, new_bandit, x, new_bandit_probs):
for i in range(N_episodes):
if i == x:
new_bandit_probs.append(bandit_probs, new_bandit)
return(new_bandit_probs)

Answer 1

返回值在for循环中。它在i从0增加到1之前立即返回。如果是x!=0，则返回空列表。

将其移出for循环:

def update_bandit_probs (bandit_probs, N_episodes, new_bandit, x, new_bandit_probs):
for i in range(N_episodes):
if i == x:
new_bandit_probs.append(bandit_probs, new_bandit)
return(new_bandit_probs)

Answer 2

你的代码不工作，因为你的return是在你的for循环的第一次迭代之后设置的。

另外，你的new_bandit_probs是空的，所以在第一次迭代后停止并返回一个空列表给出…一个空列表。修改如下:

import numpy as np
bandit_probs = [0.1, 0.4, 0.9] 
N_bandits = len(bandit_probs)
N_experiments = 1 
N_episodes = 100 
new_bandit = np.random.random ()
x = np.random.randint(0, N_episodes)
def update_bandit_probs (bandit_probs, N_episodes, new_bandit, x):
for i in range(N_episodes):
if i == x:
bandit_probs.append(new_bandit)
return bandit_probs
print (update_bandit_probs (bandit_probs, N_episodes, new_bandit, x))

输出:

[0.1, 0.4, 0.9, 0.4026139866070344]

你也可以在单行中这样做:

def update_bandit_probs(v, n, c, x):
return v+[c for i in range(n) if x == i]
print (update_bandit_probs(bandit_probs, N_episodes, new_bandit, x))