如何切掉字符串中的最后两个字符然后转换为双精度值？

Question

I'm trying to do a field calculation in ArcMap from one field to another. I need to slice off the last two characters of one field, and convert to float (or double).

I'm trying to do this:

float(!StatedArea![-2])

My starting values (from the StatedArea field) are like this:
12.99 a
0.2377 a
0.0041 a

I just want to take off the space and the "a".

All I'm getting is ERROR 000539, with this message "ValueError: could not convert string to float"

Any ideas what the issue could be?

Answer 1

float(!StatedArea![:-2])

should work. You might want to revisit list indexing in python: https://www.tutorialspoint.com/python/python_lists.htm

Answer 2

As already stated [:-2] will discard two last characters of str . I want to note that Python has no built-in double type. According to documentation in most implementations, Python's float is equivalent to C double . Therefore if you will use float , you might expect precision equivalent to double .