Python 3.4 Beta 1 Released

89 points by alxv 12 years ago | 28 comments

Wow, I haven't heard of pathlib [1] before now, but it looks awesome! In particular, using the slash operator to join paths is brilliant.

    >>> p = PurePath('/etc')
    >>> p / 'init.d' / 'apache2'
    PurePosixPath('/etc/init.d/apache2')

[1]: http://docs.python.org/3.4/library/pathlib.html

yareally 12 years ago | |

Scala does something similarly neat with using #| for piping system commands.

Slash for Scala is not used by default though for path joining, but it can be by adding an implicit function:

  implicit def slash(str: String) = new { def /(joinStr: String) = str + java.io.File.separatorChar + joinStr} 

  val joinedStr = "abc"/"def"/"ghi"
  > joinedStr : java.lang.String = abc/def/ghi

Shell friendly syntax can be used for stdin/stdout in Scala as well (already in the stdlib with no implicits required):

#< Redirect STDIN

#> Redirect STDOUT

#>> Append to STDOUT

#&& Create an AND list

#!! Create an OR list

http://stackoverflow.com/questions/12772605/scala-shell-comm...

http://alvinalexander.com/scala/scala-execute-exec-external-...

d0mine 12 years ago | | |

There are Plumbum shell combinators in Python http://plumbum.readthedocs.org/en/latest/

thristian 12 years ago | |

I hadn't heard of it either, although I have played with Twisted's FilePath[1] class previously.

I didn't really understand the attraction of an OO filesystem API until I actually used it in anger and realised how handy it was that all the relevant functions were on the object I was messing with, instead of arbitrarily divided between the "os" and "os.path" modules.

Some (hopefully constructive) suggestions for the pathlib API:

- Python 3 dicts ditched .iterkeys(), .itervalues() and .iteritems(); why does pathlib use the clumsy .iterdir() when it could just be called .children?

- Like many Python programmers (I assume), I'm more familiar with POSIX command-line tools than I am with POSIX APIs. Command-line tools generally have an option to control whether they dereference symlinks (cp -L, find -L, etc) rather than having a separate. parallel tool that does the same thing. I think it would be neater if .lstat() and .lchmod() were removed in favour of a "follow_symlinks" parameter to .stat() and .chmod() (and .is_dir() and .touch() and .owner(), and, and, and..)

- If you're going to have convenience functions that pick out interesting bits from the .stat() return value, I would find .size() far more practical than .is_socket()

[1]: http://twistedmatrix.com/documents/current/api/twisted.pytho...

yen223 12 years ago | |

One of the many things I like about Python is their pragmatic approach to operator overloading. Well, their pragmatic approach to everything, really.

bodyfour 12 years ago | |

FWIW, the boost::filesystem C++ package uses the / operator in the same way

avdd_ 12 years ago | |

No one objected to using "pure" instead of the more common "abstract" (which is the actual antonym of "concrete") ?? Why do people do this?

CUViper 12 years ago | | |

Concrete paths inherit from pure paths - this would be quite strange using antonyms. This isn't like an "abstract" base class. It's a full class on its own, which is extended by another.

Anyway, I think it's meant to be "pure" like pure functions, generally having no side effects or external inputs.

https://en.wikipedia.org/wiki/Pure_function

reinhardt 12 years ago | |

The precursor path library [1] by J. Orendorff had the slash operator overloading trick a decade (or more) ago.

[1] https://pypi.python.org/pypi/path.py/1.2

Flimm 12 years ago | |

I thought operator overloading like that was considered bad practise. It seems to me that the + operator should have been overloaded, not the / operator.

computerhead 12 years ago |

Been using python for 7+ years now. Does everyone really think people are willing to adopt 3.x anything...? The reality of it is every place I have worked (and currently working at). Is bound by 3rd party tools and what ever interpreter they built against. Mostly that 2.6,2.7 right now. And it does not look like anyone will be switching anytime soon.

Features look great, cant wait to "play" with them. But that;s about all. Play.

makmanalp 12 years ago |

> a new C API for implementing custom memory allocators

Wow. This'll lead to some interesting hacks, I think.

amirouche 12 years ago | |

Finally all the hacks done internaly by some big Python company is released in the wild and not by them. Check out the presentation by the creator (in french) https://github.com/haypo/conf/blob/master/2013-PyconFR-Stras...

haypo 12 years ago | | |

I started the development of tracemalloc at Wyplay, but I rewrote all the code for the version included in Python 3.4: complelty different API, you get different data, new implementation, etc. The old code: https://github.com/wyplay/pytracemalloc/

The PEP 445 (malloc API) also allows to plug hooks on memory allocators at runtime, instead of having to recompile Python for that.

haypo 12 years ago | |

tracemalloc is the first user of the PEP 445 (malloc API), but I wrote another toy: https://bitbucket.org/haypo/pyfailmalloc

"Debug tool for Python injecting memory allocation faults to simulate a low memory system to test how your application handles MemoryError exceptions."

the1 12 years ago |

isn't 2.7 the best python still because twisted?

simonw 12 years ago | |

The most exciting feature in 3.4 (at least in my opinion) is the addition of asyncio to the standard library, which aims to provide a standard event loop which libraries like Twisted can then use to make themselves interoperable with other async Python solutions:

http://www.python.org/dev/peps/pep-3156/

"The event loop is the place where most interoperability occurs. It should be easy for (Python 3.3 ports of) frameworks like Twisted, Tornado, or even gevents to either adapt the default event loop implementation to their needs using a lightweight adapter or proxy, or to replace the default event loop implementation with an adaptation of their own event loop implementation. (Some frameworks, like Twisted, have multiple event loop implementations. This should not be a problem since these all have the same interface.)"