RPython copy string with quotes from R to Python

问题

I have trouble copying a string from R to a string in Python using RPython. I know the basic steps of doing it if the string does not have quotes but it gives error if the string has quotes.

For example:

test <- "byte"
python.assign("string",test)
python.exec("print(string)")

Works fine and prints: byte

However,

test <- "'byte'"
python.assign("string",test)

gives error:

File "<string>", line 2
    string =' [ "'byte'" ] '
                     ^
SyntaxError: invalid syntax

If i try to escape quote characters:

test <- "\'byte\'"
python.assign("string",test)

same error:

File "<string>", line 2
    string =' [ "'byte'" ] '
                     ^
SyntaxError: invalid syntax

Or if I change internal single quotes to double quotes:

test <- "\"byte\""
python.assign("string",test)
Error in python.exec(python.command) : 
  Expecting , delimiter: line 1 column 6 (char 5)

Any ideas what am I missing, or some direction where to look ?

Thank you

回答1:

I'm also searching for good answer for this question. I can suggest workaround only:

Your example:

library('rPython')
python.exec("string=chr(39).join(['byte'])")
python.get("string")
[1] "byte"
# Alternatively: python.exec("string=chr(39) + \"byte\" + chr(39)")
# to get: [1] "'byte'"

Something more complex: Suppose 'I want' "something" like 'this'

library('rPython')
python.exec("string=\"Suppose \" + chr(39) + \"I want\" + chr(39) + \" \" + chr(34) + \"something\" + chr(34) + \" like \" + chr(39) + \"this\" + chr(39)")
python.get("string")
[1] "Suppose 'I want' \"something\" like 'this'"

Another example:

library('rPython')
python.exec("myCommand=\"gdal_translate -of GTiff -ot Int16 -a_nodata \" + chr(39) +\"-32768\" + chr(39) + \" NETCDF:\" + chr(39) + \"inputFile\" + chr(39) + \":Soil_Moisture \" + chr(39) + \"outputFile\" + chr(39)")
python.get("myCommand")
[1] "gdal_translate -of GTiff -ot Int16 -a_nodata '-32768' NETCDF:'inputFile':Soil_Moisture 'outputFile'"

回答2:

Borrowing from @matandked, you could replace single quotes with chr(39) using gsub:

library(rPython)

test <- "'byte'"

python.assign("string", gsub("\\'", "' + chr(39) + '", test))
python.get("string")

# [1] "'byte'"

There may be unintended consequences, but python.assign could be modified in a similar fashion:

python.assign <- function (var.name, value, ...) 
{
  value <- gsub("\\'", "' + chr(39) + '", value) ## Added this line...
  value <- toJSON(value, collapse = "", ...)
  python.command <- c(paste(var.name, "='", value, "'", sep = " "), 
                      paste(var.name, "= json.loads(", var.name, ")", sep = ""), 
                      paste("if len(", var.name, ") == 1:", sep = ""), paste("    ", 
                                                                             var.name, "=", var.name, "[0]"))
  python.command <- paste(python.command, collapse = "\n")
  python.exec(python.command)
  invisible(NULL)
}


## Now there's no need to substitute single quotes:
python.assign("string", test)
python.get("string")

# [1] "'byte'"

来源：https://stackoverflow.com/questions/28884625/rpython-copy-string-with-quotes-from-r-to-python

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