====== Python ======

  * [[:Python virtual environment recipe|]]
  * [[:python:colorization_and_tab_completion_for_the_python_shell|Colorization and tab completion for the python shell]]
  * [[:python:defer_to_another_program_in_the_path_if_available|Defer to another program in the PATH, if available]]
  * [[:python:socksv4_proxy|SOCKSv4 proxy]] - Simple proxy in pure python.
  * [[:python:virtualenv|]] - A recipe to download and deploy Python 2.7 in your home directory without dependencies (except gcc)
  * [[:python:optparse|]]
  * [[:python:intvectorrange|IntVectorRange]]
  * [[:python:progress_bar|Progress bar]]
  * [[:python:simple_dyndns_updater|Simple DynDNS updater]]

<code python>
# use this like a dictonary (d['thing']) OR an object (d.thing)
class DictObject(dict):
    def __getattribute__(self,k): return self[k]
    def __setattribute__(self,k,v): self[k]=v

from datetime import datetime
def timestamp(): return datetime.now().strftime("%Y%m%d-%H%M%S")

def avg(v): return sum(v)/len(v)
def stdev(v): return math.sqrt(sum(x*x for x in v) / len(v) - (avg(v) ** 2))
def pct_diff(a,b): return (a/b)-1
def product(L): return reduce(lambda x,y: x*y, L, 1)

def ping(host,timeout=1):
    ret = subprocess.call(['ping','-c1','-W',str(timeout),host],stdout=open('/dev/null', 'w'))
    return ret==0

from timeit import Timer
t = Timer("test()", "from __main__ import test")
print t.timeit()

def shred_unicode(s):
    return unicodedata.normalize('NFKD', s.decode("utf-8")).encode('ascii','ignore')

# divide a list into equal pieces.
# chunk ranges from 0 to num_chunks-1
def divide_list(lst,chunk,num_chunks):
    i = int( float(chunk)/num_chunks*len(lst) )
    j = int( float(chunk+1)/num_chunks*len(lst) )-1
    return lst[i:j]

import itertools
def sliding_window(seq, n=2, pad_value=None, pad_left=0, pad_right=0):
    "Returns a sliding window (of width n) over data from the iterable."
    "Can optionally pad the window left and right."
    it = itertools.chain(
        itertools.repeat(pad_value,pad_left),
        seq,
        itertools.repeat(pad_value,pad_right),
    )
    #it = iter(seq)
    result = tuple(itertools.islice(it, n))
    if len(result) == n:
        yield result
    for elem in it:
        result = result[1:] + (elem,)
        yield result

def open_dash(filename,mode='r',bufsize=-1):
    if filename == '-':
        if 'w' in mode  or  'a' in mode: return sys.stdout
        elif 'r' in mode:                return sys.stdin
        else:                            raise Exception("Bad mode")
    else:
        return open(filename,mode,bufsize)

# allows you to put color codes in backticks and have them turned into escape codes
# example: colorize("`31`red `44`on blue`` reset")
# if enable is set to False, then backticked numbers are merely removed instead of being colorized
def colorize(s,enable=True): return re.sub('`(.*?)`','\x1b[\\1m',s) if enable else re.sub('`(.*?)`','',s)

# a decorator that puts the given function into a dictionary, changing its name:
heuristics = {}
def heuristic(func):
    name = func.__name__.replace('gadget_is_','').replace('gadget_','').replace('_','-')
    heuristics[name]=func
    return func

# unlike set(), this is order preserving
def uniq(seq, idfunc=None):
    seen = set()
    for item in seq:
        marker = idfunc(item) if idfunc else item
        if marker not in seen:
            seen.add(marker)
            yield item


</code>

Drop into python shell:

<code python>
import code
code.interact(local=locals())

</code>

<code python>
class ConsoleThrobber(object):
    def __init__(self,chars='/\\'):
        self.chars=chars
        self.i=0
    def __call__(self):
        sys.stdout.write("\r" + self.chars[self.i])
        sys.stdout.flush()
        self.i = (self.i + 1) % len(self.chars)

def workload():
    throb = ConsoleThrobber("\\|/-")
    while True:
        # ... do stuff ...
        throb()

def recognize_type(v):
    if re.match(r'\d+$',v):
        return int(v)
    if re.match(r'\d+\.\d*$',v):
        return float(v)
    return v

</code>

Parse tab-delimited tables, especially pasted from excel:

<code python>
def recognize_type(v):
    try: return float(v)
    except ValueError: pass

    try: return int(v)
    except ValueError: pass

    return v

def parse_table(table_tsv, xform=recognize_type):
    table_rows = table_tsv.strip().split("\n")

    table = {}

    col_headers = table_rows[0].split("\t")[1:]
    row_headers = [x.split("\t")[0] for x in table_rows[1:]]
    for row_header,row in zip(row_headers,table_rows[1:]):
        values = row.split("\t")[1:]
        table[row_header] = { 'name' : row_header }
        for (col_header,value) in zip(col_headers,values):
            if xform: value = xform(value)
            table[row_header][col_header] = value
    return (row_headers,col_headers,table)

engines_tsv = """name    cost    mass    thrust    TWR    Isp_atm    Isp_vac
LV-1R Liquid Fuel Engine    650    0.03    4    13.6    220    290
O-10 MonoPropellant Engine    800    0.09    20    22.7    220    290
Rockomax 24-77    480    0.09    20    22.7    250    300
Rockomax Mark 55 Radial Mount Liquid Engine    850    0.9    120    13.6    290    320
LV-1 Liquid Fuel Engine    350    0.03    4    13.6    220    290
Rockomax 48-7S    300    0.1    30    30.6    300    350
LV-T30 Liquid Fuel Engine    850    1.25    215    17.5    320    370
LV-T45 Liquid Fuel Engine    950    1.5    200    13.6    320    370
LV-909 Liquid Fuel Engine    750    0.5    50    10.2    300    390
R.A.P.I.E.R. Engine    3600    1.75    175    10.2    320    360
Toroidal Aerospike Rocket    3850    1.5    175    11.9    388    390
Rockomax "Poodle" Liquid Engine    1600    2    220    11.2    270    390
Rockomax "Mainsail" Liquid Engine    5650    6    1500    25.5    320    360
Rockomax "Skipper" Liquid Engine    2850    3    650    22.1    320    370
LV-N Atomic Rocket Motor    8700    2.25    60    2.7    220    800
LFB KR-1x2    16400    10    2000    20.4    320    360
Kerbodyne KR-2L Advanced Engine    20850    6.5    2500    39.2    320    380
S3 KS-25x4 Engine Cluster    32400    9.75    3200    33.5    320    360
"""

(engine_names,fields,engines) = parse_table(engines_tsv, recognize_type)


</code>