相当于R中的get（）的python（=使用字符串检索符号的值）

Question

In R, the get(s) function retrieves the value of the symbol whose name is stored in the character variable (vector) s , eg

X <- 10
r <- "XVI"
s <- substr(r,1,1) ## "X"
get(s)             ## 10

takes the first symbol of the Roman numeral r and translates it to its integer equivalent.

Despite spending a while poking through R-Python dictionaries and Googling various combinations of "metaprogramming", "programming on the language", "symbol", "string", etc., I haven't come up with anything. (I am a very experienced R user and a novice Python user.)

(I know the example above is a (very!) poor way to approach the problem. I'm interested in the general answer to this question, not specifically in converting Roman numerals to integers ...)

Answer 1

You can use locals :

s = 1
locals()['s']

EDIT:

Actually, get in R is more versatile - get('as.list') will give you back as.list . For class members, in Python, we can use getattr ( here ), and for built-in things like len , getattr(__builtins__, 'len') works.

Answer 2

Use the eval function, which evaluates a string as an expression.

X = 10
r = "XVI"
v = eval(r[0])

Important note: eval() evaluates any code that can be used in an expression, not just variables. Do not use it directly in conjunction with user input, which could risk a security vulnerability.