多行字符串文字解析

Question

I have tried the following in Python's Interactive console:

>>> """"string"""
'"string'
>>> """"string""""
SyntaxError: EOL while scanning string literal

I expect the latter case """"string"""" to return '"string"' because I have three quotes at the start and three quotes at the end. How does Python interpret it?

Answer 1

Python is interpreting it as:

 """"string""" "                                                                                                                   "
#^^^These three " to start the string literal. The next one counts in the string.
#The three last ones after the last one are counted as the end.

Notice the straying " .

You can just do:

'''"string"'''

Answer 2

It sees the triple-quoted string """"string""" , followed by a non-triple-quoted string that doesn't complete by EOL, " .

The tokenize module can show you what it's doing:

s = '""""string""""'
g = tokenize.generate_tokens(io.StringIO(s).readline)
t = list(g)
print(t)

This prints a STRING token with '""""string"""' , then an ERRORTOKEN token with '"' .

In general, the best way of answering any question like this when you can't figure out how to interpret the grammar (I assume you looked at the grammar first?) is to use tokenize, ast, and friends.