1. jhjaggars
  2. dictionary_switches


dictionary_switches / src / Comprehensions.rst


History: where did they come from?

They require a mind shift.

What makes them so compelling (once you 'get it')?

A two-level list comprehension using os.walk():

# Comprehensions/os_walk_comprehension.py
import os
restFiles = [os.path.join(d[0], f) for d in os.walk(".")
             for f in d[2] if f.endswith(".rst")]
for r in restFiles:

A More Complex Example


This is still under development. After finishing, it will get a full description of all parts.

# CodeManager.py
TODO: update() is still only in test mode; doesn't actually work yet.

Extracts, checks and updates code examples in ReST files.

You can just put in the codeMarker and the (indented) first line (containing the
file path) into your ReST file, then run the update program to automatically
insert the rest of the file.
import os, re, sys, shutil, inspect, difflib

restFiles = [os.path.join(d[0], f) for d in os.walk(".") if not "_test" in d[0]
             for f in d[2] if f.endswith(".rst")]

class Languages:
    "Strategy design pattern"

    class Python:
        codeMarker = "::\n\n"
        commentTag = "#"
        listings = re.compile("::\n\n( {4}#.*(?:\n+ {4}.*)*)")

    class Java:
        codeMarker = "..  code-block:: java\n\n"
        commentTag = "//"
        listings = \
            re.compile(".. *code-block:: *java\n\n( {4}//.*(?:\n+ {4}.*)*)")

def shift(listing):
    "Shift the listing left by 4 spaces"
    return [x[4:] if x.startswith("    ") else x for x in listing.splitlines()]

# TEST - makes duplicates of the rst files in a test directory to test update():
dirs = set([os.path.join("_test", os.path.dirname(f)) for f in restFiles])
if [os.makedirs(d) for d in dirs if not os.path.exists(d)]:
    [shutil.copy(f, os.path.join("_test", f)) for f in restFiles]
testFiles = [os.path.join(d[0], f) for d in os.walk("_test")
             for f in d[2] if f.endswith(".rst")]

class Commands:
    Each static method can be called from the command line. Add a new static
    method here to add a new command to the program.

    def display(language):
        Print all the code listings in the .rst files.
        for f in restFiles:
            listings = language.listings.findall(open(f).read())
            if not listings: continue
            print('=' * 60 + "\n" + f + "\n" + '=' * 60)
            for n, l in enumerate(listings):
                if n < len(listings) - 1:
                    print('-' * 60)

    def extract(language):
        Pull the code listings from the .rst files and write each
        listing into its own file.
        paths = set()
        for f in restFiles:
            for listing in language.listings.findall(open(f).read()):
                listing = shift(listing)
                path = listing[0][len(language.commentTag):].strip()
                if path in paths:
                    print("ERROR: Duplicate file name: %s" % path)
                path = os.path.join("..", "code", path)
                dirname = os.path.dirname(path)
                if dirname:
                    if not os.path.exists(dirname):
                file(path, 'w').write("\n".join(listing))

    def check(language):
        Ensure that external code files exist and check which external files
        have changed from what's in the .rst files. Generate files in the
        _deltas subdirectory showing what has changed.
        missing = []
        listings = [shift(code) for f in restFiles for code in
        paths = [os.path.normpath(os.path.join("..", "code", path)) for path in
                     for listing in listings]]
        for path, listing in zip(paths, listings):
            if not os.path.exists(path):
                code = open(path).read().splitlines()
                for i in difflib.ndiff(listing, code):
                    if i.startswith("+ ") or i.startswith("- "):
                        d = difflib.HtmlDiff()
                        if not os.path.exists("_deltas"):
                        html = os.path.join("_deltas",
                            os.path.basename(path).split('.')[0] + ".html")
                        open(html, 'w').write(d.make_file(listing, code))
                        print("change in %s; see %s" % (path, html))
        if missing:
            print("Missing", language.__name__, "files:\n", "\n".join(missing))
        return missing

    def update(language): # Test until it is trustworthy
        Refresh external code files into ReST files.
        if Commands.check(language):
            print(language.__name__, "update aborted")
        def _update(matchobj):
            listing = shift(matchobj.group(1))
            path = listing[0].strip()[len(language.commentTag):].strip()
            filename = os.path.basename(path).split('.')[0]
            path = os.path.join("..", "code", path)
            code = open(path).read().splitlines()
            return language.codeMarker + \
                "\n".join([("    " + line).rstrip() for line in listing])
        for f in testFiles:
            updated = language.listings.sub(_update, open(f).read())
            open(f, 'w').write(updated)

if __name__ == "__main__":
    commands = dict(inspect.getmembers(Commands, inspect.isfunction))
    if len(sys.argv) < 2 or sys.argv[1] not in commands:
        print("Command line options:\n")
        for name in commands:
            print(name + ": " + commands[name].__doc__)
        for language in inspect.getmembers(Languages, inspect.isclass):