在循环中重复值,直到错误消失 [英] Repeating values in loop until error disappears
问题描述
我目前正在使用for循环使用Googleway软件包对大量地址进行地理编码.最初,我遇到了"500个内部服务器错误"的问题,从而停止了循环的执行.我能够使用tryCatch()解决此问题.但是,由于这往往是暂时性错误,因此我希望函数重复抛出错误的地址,直到它接收到结果或进行任意次尝试(例如10次)为止.
I am currently using a for loop to geocode a large number of addresses using the Googleway package. Initially, I ran into issues with "500 internal server errors" stopping the execution of the loop. I was able to get around this using tryCatch(). However, since this tends to be a transient error, I would like the function to repeat the address that throws the error until it receives a result or hits some arbitrary number of attempts, let's say 10.
不幸的是,我发现tryCatch()和与之相关的文档令人困惑,所以我不知该如何做,除了使它抛出错误消息并继续前进之外,什么都不做.这是我当前的代码:
Unfortunately, I've found tryCatch() and the documentation associated with it confusing, so I'm at a loss for how to do anything other than get it to throw an error message and move on. Here is my current code:
rugeocoder.fun <- function(addr){
require(googleway)
output <- vector("list", length=length(addr))
tryCatch({
for(i in 1:length(addr)){
output[[i]] <- google_geocode(address=addr[i], key="myapikey", language="ru", simplify=T)
print(i)
}},error=function(e) output[[i]] <- "Error: reattempt")
return(output)
}
推荐答案
您可能想要分离出安全调用google_geocode()
和循环访问地址的逻辑.
You probably want to separate out the logic for calling google_geocode()
safely, and for looping over the addresses.
这是一个功能,该功能可以修改其他功能以反复调用它们,直到它们起作用为止,否则它们将失败max_attempts
次.修改其他功能的功能有时称为副词".
Here's a function that modifies other functions to call them repeatedly until they work, or they fail max_attempts
times. Functions that modify other functions are sometimes called "adverbs".
safely <- function(fn, ..., max_attempts = 5) {
function(...) {
this_env <- environment()
for(i in seq_len(max_attempts)) {
ok <- tryCatch({
assign("result", fn(...), envir = this_env)
TRUE
},
error = function(e) {
FALSE
}
)
if(ok) {
return(this_env$result)
}
}
msg <- sprintf(
"%s failed after %d tries; returning NULL.",
deparse(match.call()),
max_attempts
)
warning(msg)
NULL
}
}
尝试使用此简单函数生成随机数,如果函数太小则会抛出错误.
Try it out on this simple function that generates a random number, and throws an error if it is too small.
random <- function(lo, hi) {
y <- runif(1, lo, hi)
if(y < 0.75) {
stop("y is less than 0.75")
}
y
}
safe_random <- safely(random)
safe_random() # will sometimes work, will sometimes return NULL
safe_random(0, 10) # will usually work
在这种情况下,您想修改google_geocode()
函数.
In you case, you want to modify the google_geocode()
function.
safe_google_geocode <- safely(google_geocode)
然后遍历调用此地址的地址.
Then loop over addresses calling this.
geocodes <- lapply( # purrr::map() is an alternative
addresses,
safe_google_geocode,
key = "myapikey",
language = "ru",
simplify = TRUE
)
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