Python 3.6变量注释和数字文字

Question

In the documentation on Python in the section "What's new in Python 3.6" among other things there are presented variable annotations and using underscores in numeric literals.

However I tried shown examples and not all of them were passed.

Are these examples incomplete and do they require some additional code that is assumed under the hood?

For example this statement

primes: List[int] = []

issues

NameError: name 'List' is not defined

This statement

print( 1_000_000_000_000_000 ) 

is also considered as wrong.

Answer 1

The first case works if you first import List from typing . Most types used with type-hints aren't built-in, they need to be imported first.

The second case also works if you are running under 3.6 . On my machine it correctly prints:

Python 3.6.2 | packaged by conda-forge | (default, Jul 23 2017, 22:59:30) 
[GCC 4.8.2 20140120 (Red Hat 4.8.2-15)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> print( 1_000_000_000_000_000 ) 
1000000000000000

If the error message you receive is: SyntaxError: invalid syntax you're on 3.5 or less. If it's SyntaxError: invalid token you're not using the underscores correctly. I'm guessing you're receiving the first.

So, you might want to double check you're running with 3.6 ( python -V ).