gistfile1.py

input_text = """
initialize CSVFile from "filename" as file;
initialize RealFeatures from file as features;
set float kernel_width to 2;
initialize GaussianKernel from kernel_width as kernel;
set matrix<float> K to kernel_matrix of kernel;
"""

import re

matchers = (
    {
        "groups": ["class", "name", "parameters"],
        "regexp": "initialize (?P<class>\S+) from (?P<parameters>\S+) as (?P<name>\S+);",
        "transformer": lambda data: "%s %s = %s(%s)" % (data['class'], data['name'], data['class'], data['parameters'])
    },
    {
        "groups": ["name", "type", "value"],
        "regexp": "set (?P<type>\S+) (?P<name>\S+) to (?P<value>\S+);",
        "transformer": lambda data: "%s %s = %s" % (data['type'], data['name'], data['value']),
    },
    {
        "groups": ["name", "type", "property", "other"],
        "regexp": "set (?P<type>\S+) (?P<name>\S+) to (?P<property>\S+) of (?P<other>\S+);",
        "transformer": lambda data: "%s %s = %s.get_%s()" % (data['type'], data['name'], data['other'], data['property'])
    }
)

maps = {
    "float" : "float64_t",
    "matrix" : "SGMatrix",
    "CSVFile": "CCSVFile",
    "GaussianKernel": "CGaussianKernel"
}

for line in input_text.split("\n"):
    matched = False
    for matcher in matchers:
        match = re.compile(matcher["regexp"]).match(line)
        if match:
            data = {}
            for group in matcher["groups"]:
                data[group] = match.group(group)
                if data[group] in maps:
                    data[group] = maps[data[group]]
            print "#", line[:-1]
            print matcher["transformer"](data)
            matched = True
            break
    if not matched and line != "":
        raise Exception("Failed to parse: " + line)

Output is

# initialize CSVFile from "filename" as file
CCSVFile file = CCSVFile("filename")
# initialize RealFeatures from file as features
RealFeatures features = RealFeatures(file)
# set float kernel_width to 2
float64_t kernel_width = 2
# initialize GaussianKernel from kernel_width as kernel
CGaussianKernel kernel = CGaussianKernel(kernel_width)
# set matrix<float> K to kernel_matrix of kernel
matrix<float> K = kernel.get_kernel_matrix()