Question

I thought I’d put together a quick script to consolidate the CSS rules I have distributed across multiple CSS files, then I can minify it.

I’m new to Python but figured this would be a good exercise to try a new language. My main loop isn’t parsing the CSS as I thought it would.

I populate a list with selectors parsed from the CSS files to return the CSS rules in order. Later in the script, the list contains an element that is not found in the dictionary.

    for line in self.file.readlines():
      if self.hasSelector(line):
        selector = self.getSelector(line)
        if selector not in self.order:
          self.order.append(selector)
      elif selector and self.hasProperty(line):
        # rules.setdefault(selector,[]).append(self.getProperty(line))
        property = self.getProperty(line)
        properties = [] if selector not in rules else rules[selector]
        if property not in properties:
          properties.append(property)
        rules[selector] = properties
        # print "%s :: %s" % (selector, "".join(rules[selector]))
    return rules

Error encountered:

$ css-combine combined.css test1.css test2.css 
Traceback (most recent call last):
  File "css-combine", line 108, in <module>
    c.run(outfile, stylesheets)
  File "css-combine", line 64, in run
    [(selector, rules[selector]) for selector in parser.order],
KeyError: 'p'

Swap the inputs:

$ css-combine combined.css test2.css test1.css 
Traceback (most recent call last):
  File "css-combine", line 108, in <module>
    c.run(outfile, stylesheets)
  File "css-combine", line 64, in run
    [(selector, rules[selector]) for selector in parser.order],
KeyError: '#header_.title'

I’ve done some quirky things in the code like sub spaces for underscores in dictionary key names in case it was an issue – maybe this is a benign precaution? Depending on the order of the inputs, a different key cannot be found in the dictionary.

The script:

#!/usr/bin/env python

import optparse
import re

class CssParser:

  def __init__(self):
    self.file = False
    self.order = [] # store rules assignment order

  def parse(self, rules = {}):
    if self.file == False:
      raise IOError("No file to parse")

    selector = False
    for line in self.file.readlines():
      if self.hasSelector(line):
        selector = self.getSelector(line)
        if selector not in self.order:
          self.order.append(selector)
      elif selector and self.hasProperty(line):
        # rules.setdefault(selector,[]).append(self.getProperty(line))
        property = self.getProperty(line)
        properties = [] if selector not in rules else rules[selector]
        if property not in properties:
          properties.append(property)
        rules[selector] = properties
        # print "%s :: %s" % (selector, "".join(rules[selector]))
    return rules

  def hasSelector(self, line):
    return True if re.search("^([#a-z,\.:\s]+){", line) else False

  def getSelector(self, line):
    s = re.search("^([#a-z,:\.\s]+){", line).group(1)
    return "_".join(s.strip().split())

  def hasProperty(self, line):
    return True if re.search("^\s?[a-z-]+:[^;]+;", line) else False

  def getProperty(self, line):
    return re.search("([a-z-]+:[^;]+;)", line).group(1)


class Consolidator:
  """Class to consolidate CSS rule attributes"""

  def run(self, outfile, files):
    parser = CssParser()
    rules = {}
    for file in files:
      try:
        parser.file = open(file)
        rules = parser.parse(rules)
      except IOError:
        print "Cannot read file: " + file
      finally:
        parser.file.close()

    self.serialize(
      [(selector, rules[selector]) for selector in parser.order],
      outfile
    )

  def serialize(self, rules, outfile):
    try:
      f = open(outfile, "w")
      for rule in rules:
        f.write(
          "%s {\n\t%s\n}\n\n" % (
            " ".join(rule[0].split("_")), "\n\t".join(rule[1])
          )
        )
    except IOError:
      print "Cannot write output to: " + outfile
    finally:
      f.close()

def init():
  op = optparse.OptionParser(
    usage="Usage: %prog [options] <output file> <stylesheet1> " +
      "<stylesheet2> ... <stylesheetN>",
    description="Combine CSS rules spread across multiple " +
      "stylesheets into a single file"
  )
  opts, args = op.parse_args()
  if len(args) < 3:
    if len(args) == 1:
      print "Error: No input files specified.\n"
    elif len(args) == 2:
      print "Error: One input file specified, nothing to combine.\n"
    op.print_help();
    exit(-1)

  return [opts, args]

if __name__ == '__main__':
  opts, args = init()
  outfile, stylesheets = [args[0], args[1:]]
  c = Consolidator()
  c.run(outfile, stylesheets)

Test CSS file 1:

body {
    background-color: #e7e7e7;
}

p {
    margin: 1em 0em;    
}

File 2:

body {
    font-size: 16px;
}

#header .title {
    font-family: Tahoma, Geneva, sans-serif;
    font-size: 1.9em;
}

#header .title a, #header .title a:hover {
    color: #f5f5f5;
    border-bottom: none;
    text-shadow: 2px 2px 3px rgba(0, 0, 0, 1);
}

Thanks in advance.

Answer 1

Change

def hasProperty(self, line):
    return True if re.search("^\s?[a-z-]+:[^;]+;", line) else False

to

def hasProperty(self, line):
    return True if re.search("^\s*[a-z-]+:[^;]+;", line) else False

The hasProperty was not matching anything because \s? matches only 0 or 1 whitespace character.