Python Cheat Sheet

PythonCheatSheet.py

# Python Cheat Sheet

# List Comprehension

some_items = [{'index':i, 'value':i*i} for i in range(0,10)]
filtered_items = [item for item in some_items if item['index']%2 == 1 ]

# Dict Comprehension

some_dict = {k: v for k, v in [('a', 1), ('b', 2)] if v % 2 == 0}

# Set Comprehension

some_set = {item for item in range(0,10)}

# Generator Expression

gen = ({'index':i, 'value':i*i} for i in range(0,10))
gen.next()
for item in gen: print item

# Generator Funcion

def genGen():
    for i in range(0,10):
        yield  {'index':i, 'value':i*i}

for item in genGen(): print item

from itertools import islice
list(islice(genGen(), 4, 7))

# Zipping

[(1, 4), (2, 5), (3, 6)] == zip([1,2,3], [4,5,6])


# Spreads

def foo(a, b):
    return a-b

foo(*[2, 1]) == foo(**{'b':1, 'a':2})

# Subprocess Output Redirection

# At first issue at the terminal prompt (see http://serverfault.com/questions/59262/bash-print-stderr-in-red-color)
# color()(set -o pipefail;"$@" 2>&1>&3|sed $'s,.*,\e[31m&\e[m,'>&2)3>&1
# color python

import subprocess,sys;
# Red output
sys.stderr.write('Hello\n')
subprocess.call(["ls", "/404"])
# White output
sys.stdout.write('Hello\n')
subprocess.call(["ls", "/404"], stderr=sys.stdout.fileno())