I think it's great that for built-in types such as int and str, backward
compatibility of type hinting annotations is baked into python 3.0 to 3.4. In
fact, I *thought* python 3.0 to 3.4 would *ignore* annotations, but it
doesn't...
I'm struggling to create something backward compatible that requires the
'typing' module. For example, the following program is good in python 3.5, but
line 11 is a syntax error in python 3.4:
1 import sys
2
3 if sys.version_info[0] < 3:
4 raise RuntimeError("Must use at least python version 3")
5
6 # The 'typing' module, useful for type hints, was introduced in python
3.5
7 if sys.version_info[1] >= 5:
8 from typing import Optional
9
10
11 def divider(x: int, y: int) -> Optional[float]:
12 if y == 0:
13 return None
14 return x / y
15
16 print("22 / 7 = " + str(divider(22, 7)))
17 print("8 / 0 = " + str(divider(8, 0)))
18
When I run this program in python 3.4, I get this:
Traceback (most recent call last):
File "./ned.py", line 11, in <module>
def divider(x: int, y: int) -> Optional[float]:
NameError: name 'Optional' is not defined
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