mr.scripty 1.0b3

Use python to write configuration in zc.buildout

Contents

• Detailed Documentation

  • Supported options

  • Example usage

    • Tranforming Varnish backends for HAProxy

    • Offsetting port numbers

    • Different download links for certain architectures

    • Checking existence of directories

• Contributors

• Change history

  • 1.0b3 (2011-12-14)

  • 1.0b2 (2011-03-23)

  • 1.0b1 (2011-03-15)

• Download

• Code repository: https://github.com/collective/mr.scripty

• Questions and comments to https://github.com/collective/mr.scripty

• Report bugs at https://github.com/collective/mr.scripty

Detailed Documentation

Supported options

The recipe supports any number of options, which are Python functions. Since the ini parser used with buildout doesn’t preserve initial whitespace each line of your method should start with a … followed by the whitespace as per normal python. They will look like this

[myscripts]
recipe = mr.scripty
MAX = 10
function1 =
  ... x = range(1,int(self.MAX))
  ... return ' '.join(x)

The return value will be stored as a value in the buildout parts options which is available for replacement in other buildout parts. What is returned is always converted to a string.

As each option is a Python function, it needs to possess an acceptable function identifier (see http://docs.python.org/reference/lexical_analysis.html#grammar-token-identifier). For instance, typical buildout options with hyphens (such as environment-vars) will be invalid.

Options all in upper case are treated as string constants and added to the Recipe instance as an attribute.

These functions are actually instance methods of the instance of the scripty recipe. Methods are evaluated during the initialization of the Recipe instance, i.e. after the cfg is read but before any install or ‘update` recipe methods have been called. Method names of install, update are treated specially and not evaluated during initialization but rather during the install and update phases of building this recipe instance. These can be used as quick in-place replacement for creating a real recipe and have the same semantics as detailed in http://pypi.python.org/pypi/zc.buildout#id3. In addition any option beginning with _ is not evaluated so can be used as a private method. Since these are methods self is an available local variable which refers to the recipe instance. self.options, self.buildout and self.name are also available.

Example usage

Tranforming Varnish backends for HAProxy

Let’s say you want to transform the a varnish:backends value to what can be used inside haproxy:

>>> write('buildout.cfg',
... """
... [buildout]
... parts = scripty echobackends echorepeat
...
... [varnish]
... backends =
...         myhost.com:255.255.255.1
...     myhost2.com:125.125.125.1
...
... [scripty]
... recipe = mr.scripty
... backends =
...   ... res = ""
...   ... for line in self.buildout['varnish']['backends'].splitlines():
...   ...    if ':' not in line:
...   ...      continue
...   ...    host,dest = line.split(':')
...   ...    host = host.split('.')[0]
...   ...    res += "acl %s url_sub VirtualHostRoot/%s\\n" % (dest,host)
...   ... return res
... repeat =
...   ... opt_repeatx = int(self.options['repeatx'])
...   ... fun_repeatx = self.repeatx()
...   ... return '\\n'.join(["this is line %s"%i for i in range(1,opt_repeatx+1)])
... repeatx = return '10'
...
... [echobackends]
... recipe = mr.scripty
... install = print self.buildout['scripty']['backends']; return []
...
... [echorepeat]
... recipe = mr.scripty
... install =
...   ... script = self.buildout['scripty']
...   ... print script['repeat']
...   ... return []
... """)

Running the buildout gives us:

>>> print 'start', system(buildout)
start...
Installing echobackends.
acl host url_sub VirtualHostRoot/255.255.255.1
acl host2 url_sub VirtualHostRoot/125.125.125.1
<BLANKLINE>
Installing echorepeat.
this is line 1
this is line 2
this is line 3
this is line 4
this is line 5
this is line 6
this is line 7
this is line 8
this is line 9
this is line 10
<BLANKLINE>

From this example you’ll notice several things. Options that are part of a mr.scripty part are turned into methods of the part instance and can call each other. In addition, each method can be called from other buildout recipes by accessing the option via ${part:method} or in code via self.buildout[part][method].

Offsetting port numbers

The following example will make all the values of ports_base available with an offset added to each one

[ports_base]
instance1=8101
instance2=8102


[ports]
recipe=mr.scripty
OFFSET = 1000
init=
  ... for key,value in self.buildout['ports_base'].items():
  ...   self.options[key] = str(int(value)+int(self.OFFSET))

Different download links for certain architectures

This example usage shows how to alter download links for third-party libraries based upon whether the host platform is 32 or 64-bit. Note that the example uses Python 2.6 or later:

[buildout]
parts =
    ...
    download

[scripty]
recipe = mr.scripty
DOWNLOAD_URL_64 = http://site.com/64bit.tgz
DOWNLOAD_URL_32 = http://site.com/32bit.tgz
download_url =
... import platform
... is_64bit = any(['64' in x for x in platform.architecture()])
... return is_64bit and self.DOWNLOAD_URL_64 or self.DOWNLOAD_URL_32

[download]
recipe = hexagonit.recipe.download
url = ${scripty:download_url}

Checking existence of directories

This example tests the existence of a list of directories and selects the first one that can be found on the system. In this particular example, we look through a list of potential JDK directories, as the location will differ across Linux distributions, in order to install an egg that depends on having a Java SDK install available:

[buildout]
parts =
    ...
    jpype

[scripty]
recipe = mr.scripty
JAVA_PATHS =
    /usr/lib/jvm/java-6-openjdk
    /etc/alternatives/java_sdk
    ${buildout:directory}
java =
    ... import os
    ... paths = self.JAVA_PATHS.split('\n')
    ... exists = [os.path.exists(path) for path in paths]
    ... return paths[exists.index(True)]

[java-env]
JAVA_HOME = ${scripty:java}

[jpype]
recipe = zc.recipe.egg:custom
egg = JPype
find-links =
    http://aarnet.dl.sourceforge.net/project/jpype/JPype/0.5.4/JPype-0.5.4.1.zip
environment = java-env

Contributors

“[e-mail]”, Dylan Jay

Change history

1.0b3 (2011-12-14)

• fix indenting issues [djay]

• init is handled as special function where result isn’t stored [djay]

1.0b2 (2011-03-23)

• Allow constants if option all uppercase [djay]

• function return values converted to strings or empty string if None [djay]

1.0b1 (2011-03-15)

• Initial version [“Dylan Jay”]

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