# I try to run:
import os
os.system(r"start C:\Windows\System32\")
# But I get an Exception:
SyntaxError: EOL while scanning string literal
# A string after “r” means the string's original meaning. But……

You can't end a string with a bare backslash, not even an raw string.

See the FAQ:

https://docs.python.org/3/faq/design.html#why-can-t-raw-strings-r-strings-end-with-a-backslash

Also documented here:

https://docs.python.org/dev/reference/lexical_analysis.html#string-and-bytes-literals

Previous issues: #1271 and #31136

Yep.

An EOL while scanning string literal error indicates that the Python interpreter expected a particular character or set of characters to have occurred in a specific line of code, but that those characters were not found before the end of the line . This results in Python stopping the program execution and throwing a syntax error . In most cases, this is  due to the following reasons:

    Missing quotes
    Strings spanning multiple lines

Strings can't normally span multiple lines. If you don't want the string to appear on multiple lines but you want to initialize it on multiple lines (so you can read it more easily), you can "escape" the newline by putting a backslash before the newline. If you want it to appear on multiple lines, you can use triple quotes around the string.

http://net-informations.com/python/err/eol.htm