from itertools import izip, imap, count, ifilter
import re
def cat(fname):
return file(fname).xreadlines()
class grep:
"""keep only lines that match the regexp"""
def __init__(self,pat,flags=0):
self.fun = re.compile(pat,flags).match
def __ror__(self,input):
return ifilter(self.fun,input)
class tr:
"""apply arbitrary transform to each sequence element"""
def __init__(self,transform):
self.tr=transform
def __ror__(self,input):
return imap(self.tr,input)
class printlines_class:
"""print sequence elements one per line"""
def __ror__(self,input):
for l in input:
print l
printlines=printlines_class()
class terminator:
"""to be used at the end of a pipe-sequence"""
def __init__(self,method):
self.process=method
def __ror__(self,input):
return self.process(input)
# those objects transform generator to list, tuple or dict
aslist = terminator(list)
asdict = terminator(dict)
astuple = terminator(tuple)
# this object transforms seq to tuple sequence
enum = terminator( lambda input: izip(count(),input) )
#######################
# example 1: equivalent to shell grep ".*/bin/bash" /etc/passwd
cat('/etc/passwd') | tr(str.rstrip) | grep('.*/bin/bash') | printlines
#######################
# example 2: get a list of int's methods beginning with '__r'
dir(int) | grep('__r') | aslist
#######################
# example 3: useless; returns a dict {0:'l',1:'a',2:'m',3:'b',4:'d',5:'a'}
'lambda' | enum | asdict
