python - 这段代码中 R 双括号的 Python 等价物是什么？

Question

我正在尝试将此 R 代码翻译成 Python。我不明白的部分是 EventTime[[i]] = c(timeList,cutoff[i]) 中的双括号的作用。 EventTime 一开始也是空的。

n = 50
cutoff = runif(n,min = 2, max = n)
rvStore = rgeom(1000,prob=0.2)+runif(1000) 
rvPosn = 0
EventTime = list()
for(i in 1:n){
        rvPosn = rvPosn + 1
        intArrival = currentTime = rvStore[rvPosn] 
        timeList = c()
        while(currentTime < cutoff[i]){
          timeList = c(timeList,currentTime)
          rvPosn = rvPosn + 1
          intArrival = rvStore[rvPosn]
          currentTime = currentTime + intArrival
        }
        EventTime[[i]] = c(timeList,cutoff[i])
}

在 Python 中，这似乎是:

n = 50
cutoff = np.random.uniform(n, 2, n)
rvStore = np.random.geometric(0.2, size=1000) + np.random.uniform(size=1000)
rvPosn = 0
EventTime = []
for i in range(n):
    rvPosn = rvPosn + 1
    intArrival = currentTime = rvStore[rvPosn]
    timeList = []
    while(currentTime < cutoff[i]):
        timeList.append(currentTime)
        rvPosn = rvPosn + 1
        intArrival = rvStore[rvPosn]
        currentTime = currentTime + intArrival
    EventTime[i] = # What should this be??

Answer 1

首先，让我们解决 R 术语:EventTime 是一个列表，这意味着为了获取/修改特定条目，需要双括号表示法，看

EventTime[1] # returns the sub-list consisting of the first entry
EventTime[[1]] # actually returns the content of the first entry

关于列表为空，我相信内部 EventTime[[i]] = ... 重新声明列表。考虑以下示例:

test_list <- list()
test_list[[2]] <- "Hello"
test_list
# [[1]]
# NULL
# 
# [[2]]
# [1] "Hello"

现在转到 Python，这里是您的代码，稍作修改:

# import numpy as np

# Set seed for replicating purposes
np.random.seed(seed=123)

n = 50
cutoff = np.random.uniform(n, 2, n)
rvStore = np.random.geometric(0.2, size=1000) + np.random.uniform(size=1000)
rvPosn = -1    # Indexing starts at 0 in python, hence set to -1 here.
EventTime = []
for i in range(n):
    rvPosn += 1
    intArrival = currentTime = rvStore[rvPosn]
    timeList = list()
    while currentTime < cutoff[i]:
        timeList.append(currentTime)
        rvPosn += 1
        intArrival = rvStore[rvPosn]
        currentTime += intArrival
    timeList.append(cutoff[i])
    if EventTime:    # If EventTime is not an empty list
        EventTime.extend(timeList)
    else:
        EventTime = timeList

返回

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24.355894013541274, 35.01146129732167, 5.124703951840116, 14.363253208503512, 16.309525389507478, 18.528987173959504, 23.29284377045799, 24.890883780006522, 29.535137265785206, 2.5952858934976852, 5.728905923419344, 7.117320170377532, 1.9721335039087353, 4.399854319017098, 4.680319126213774, 5.927506880622765, 8.538281200589076, 12.266138445034487, 13.809543069603565, 16.820745079630505, 21.576445190048975, 23.555142365970948, 25.911839557551843, 2.808757370538774, 8.660344040099975, 10.6595453026846, 20.050258313978663, 1.4493841923188184, 2.9922102823176746, 10.144665976622084, 11.625641977204268, 17.90262286399708, 34.7395552145328, 44.45031703619381, 6.081684662113023, 21.091770081033683, 24.952313568577566, 34.7702968726246, 2.934088705573286, 15.006634238546495, 16.401392887767344, 29.82958683130629, 30.088341826225673, 8.417160421598439, 1.3022043980030458, 7.0349316671907225, 8.214984157825558, 14.850358994002711, 16.592568228998775, 17.773021694715535, 19.9949664624289, 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