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Merged
merged 9 commits into from
Sep 26, 2017
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README.md: rearrange first paragraph to be more friendly #4002

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77938e0
README.md: rearrange first paragraph to be more friendly
elazarg Sep 25, 2017
43f3988
Demonstration for comments and new style annotations
elazarg Sep 25, 2017
998e4c3
Remove erroneous statement
elazarg Sep 25, 2017
932aa4d
Remove variable annotations. Change description of annotations
elazarg Sep 25, 2017
5422d17
move PEP-484 link and type comment; deep link for Python 2
elazarg Sep 26, 2017
8ed7f76
Remove mention of LXML
elazarg Sep 26, 2017
db8e6df
Fix type comment and give better example
elazarg Sep 26, 2017
e2b9b94
s/str/bool/
elazarg Sep 26, 2017
09c1055
Wrap long line.
gvanrossum Sep 26, 2017
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37 changes: 24 additions & 13 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -25,17 +25,8 @@ What is mypy?
-------------

Mypy is an optional static type checker for Python. You can add type
hints to your Python programs using the standard for type
annotations introduced in Python 3.5 ([PEP 484](https://www.python.org/dev/peps/pep-0484/)), and use mypy to
type check them statically. Find bugs in your programs without even
running them!

The type annotation standard has also been backported to earlier
Python 3.x versions. Mypy supports Python 3.3 and later.
XML based reports do not work on Python 3.3 and 3.4 on Windows.

For Python 2.7, you can add annotations as comments (this is also
specified in [PEP 484](https://www.python.org/dev/peps/pep-0484/)).
hints to your Python programs, and use mypy to type check them statically.
Find bugs in your programs without even running them!

You can mix dynamic and static typing in your programs. You can always
fall back to dynamic typing when static typing is not convenient, such
Expand All @@ -47,7 +38,8 @@ Here is a small example to whet your appetite:
from typing import Iterator

def fib(n: int) -> Iterator[int]:
a, b = 0, 1
a: int = 0
b: int = 1
while a < n:
yield a
a, b = b, a + b
Expand All @@ -56,6 +48,24 @@ def fib(n: int) -> Iterator[int]:
Mypy is in development; some features are missing and there are bugs.
See 'Development status' below.

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Good move 🚜

-----------
For Python 3, you can add type hints to your Python programs using the standard for type
annotations ([PEP 484](https://www.python.org/dev/peps/pep-0484/)).

For Python 2.7, you can add annotations as comments (this is also
specified in [PEP 484](https://www.python.org/dev/peps/pep-0484/)):
```python
from typing import Iterator

def fib(n): # type: int -> Iterator[int]
a = 0 # type: int
b = 1 # type: int
while a < n:
yield a
a, b = b, a + b
```


Requirements
------------
Expand Down Expand Up @@ -158,7 +168,8 @@ In Windows, the script is generally installed in
C:\>\Python34\python \Python34\Scripts\mypy PROGRAM

If you are on Windows using Python 3.3 or 3.4, and would like to use XML reports
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If #4007 gets merged before this, this sentence can be removed, as there are wheels for all Python versions on Windows now, and installing via test-requirements will "just work".

download LXML from [PyPi](https://pypi.python.org/pypi/lxml).
download LXML from [PyPi](https://pypi.python.org/pypi/lxml).
XML based reports do not work on Python 3.3 and 3.4 on Windows.
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They do work, but only if you have LXML installed. The last sentence can be deleted.


### Working with `virtualenv`

Expand Down