Fix compatibility issues with Python >= 3.6

[egao1980]

• \$ and \. trigger SyntaxError in Python 3.6
• % format operator is not compatible with Python 3.6

[ShaneHarvey]

Hi @egao1980. What do you mean "$ and . trigger SyntaxError in Python 3.6"?

$ python3.6
Python 3.6.5 (v3.6.5:f59c0932b4, Mar 28 2018, 05:52:31)
[GCC 4.2.1 Compatible Apple LLVM 6.0 (clang-600.0.57)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> {"$regex": "^(?!.*\$)"}
{'$regex': '^(?!.*\\$)'}
>>> ^D
$ python3.7
Python 3.7.0b4 (v3.7.0b4:eb96c37699, May  2 2018, 04:13:13)
[Clang 6.0 (clang-600.0.57)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> {"$regex": "^(?!.*\$)"}
{'$regex': '^(?!.*\\$)'}
>>>

[egao1980]

Markdown ate my slashes. Python 3.6 do not allow non standard escapes. So we need to use raw strings or escape the backslash

[ShaneHarvey]

But what problem are you trying to solve? This code already works on all versions of Python (besides benchmark.py).

[egao1980]

This breaks strict tests with 'python -We ...'

python3.6 -We
Python 3.6.5 (default, Mar 30 2018, 06:42:10)
[GCC 4.2.1 Compatible Apple LLVM 9.0.0 (clang-900.0.39.2)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> '\s'
  File "<stdin>", line 1
SyntaxError: invalid escape sequence \s
>>> '\$'
  File "<stdin>", line 1
SyntaxError: invalid escape sequence \$
>>> '\.'
  File "<stdin>", line 1
SyntaxError: invalid escape sequence \.

[ShaneHarvey]

This should be {0}{1} to support python 2.6. Or you can just use % formatting as before which is valid on all python versions.

[egao1980]

Thanks, will make sure that 2.6 version works.

[ShaneHarvey]

Ah I see. That is a problem. My only comment is on the change to benchmark.py.

[ShaneHarvey]

@egao1980 Thanks!