On 23.01.17 01:30, Soni L. wrote:
On 22/01/17 08:54 PM, Serhiy Storchaka wrote:
On 23.01.17 00:45, Soni L. wrote:
I've been thinking of an Immutable Builder pattern and an operator to go with it. Since the builder would be immutable, this wouldn't work:
long_name = mkbuilder() long_name.seta(a) long_name.setb(b) y = long_name.build()
I think the more pythonic way is:
y = build(a=a, b=b)
A Builder pattern is less used in Python due to the support of keyword arguments.
I guess you could do something like this, for an IRC bot builder:
fnircbotbuilder = mkircbotbuilder(network="irc.freenode.net", port=6697, ssl=true) mainbot = mkircbotbuilder(parent=fnircbotbuilder, # ??? channels=["#bots"]).build() fndccbotbuilder = mkircbotbuilder(parent=fnircbotbuilder, dcc=true, channeldcc=true) dccbot = mkircbotbuilder(parent=fndccbotbuilder, channels=["#ctcp-s"]).build() otherircbotbuilder = mkircbotbuilder(parent=fndccbotbuilder, network="irc.subluminal.net") # because we want this whole network otherbot = mkircbotbuilder(parent=otherircbotbuilder, channels=["#programming"]).build() # to use DCC and channel DCC
But this would be cleaner:
botbuilder = mkircbotbuilder().network("irc.freenode.net").port(6697).ssl(true) mainbot = botbuilder.channels(["#bots"]).build() botbuilder .= dcc(true).channeldcc(true) dccbot = botbuilder.channels(["#ctcp-s"]).build() botbuilder .= network("irc.subluminal.net") otherbot = botbuilder.channels(["#programming"]).build()
In Python you can save common options in a dict and pass them as var-keyword argument. Or use functools.partial. In any case you don't need a builder class with the build method and a number of configuring methods. It can be just a function with optional keyword parameters. A Builder pattern is often used in languages that don't support passing arguments by keyword and partial functions. Python rarely needs the purposed class implementing a Builder pattern. Actually a Builder pattern is built-in in the language as a part of syntax.