Python snippets (1)

with open('/etc/passwd','r') as f:

    for eachLine in f:

        print eachLine,

>>> assert 1==0, "one does not equal zero silly"

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

AssertionError: one does not equal zero silly

def assert(expr, args=None):

    if __debug__ and not expr:

        raise AssertionError, args

class NetworkError(IOError):

    pass

class FileError(IOError):

    pass

"access" in dir(os)

#!/usr/bin/env python

from time import ctime, sleep

def tsfunc(func):

    def wrappedFunc():

        print '[%s] %s() called' %(ctime(), func.__name__)

        return func()

    return wrappedFunc

@tsfunc

def foo():

    pass

foo()

sleep(4)

for i in range(2):

    sleep(1)

    foo()

Output:

➜  core_python git:(dev) ✗ python deco.py

[Sat Aug 22 20:36:13 2015] foo() called

[Sat Aug 22 20:36:18 2015] foo() called

[Sat Aug 22 20:36:19 2015] foo() called

def tupleVarArgs(arg1, arg2 = 'defaultB', *theRest):

    'Display regular args and non-keyword variable args'

    print 'formal arg 1:', arg1

    print 'formal arg 2:', arg2

    for eachArg in theRest:

        print 'another arg:', eachArg

if __name__ == '__main__':

    tupleVarArgs('acg')

    tupleVarArgs('23',5.67)

    tupleVarArgs('adf','123',67,90)

#!/usr/bin/env python

from random import randint

'Demonstrate filger'

def testFilter():

    def odd(n):

        return n%2

    allNums = []

    for eachNum in range(9):

        allNums.append(randint(1,99))

    print filter(odd, allNums)

def testFilterLambda():

    'Using lambda to re-write the code'

    allNums = []

    for eachNum in range(9):

        allNums.append(randint(1,99))

    print filter(lambda n:n%2, allNums)

def testFilterList():

    allNums = []

    for eachNum in range(9):

        allNums.append(randint(1, 99))

    print [n for n in allNums if n%2]

def testFilterParseList():

    print [n for n in [randint(1, 99) for i in range(9)] if n%2]

def testMap():

    print map((lambda x:x+2),[0,1,2,3,4,5,6])

def testMapMultiList(): #just he hadoop map/reduce

    print map((lambda x,y:x+y), [1,3,5],[2,4,6])

def testMapNoneList(): #Just like zip function

    print map(None, [1,3,5],[2,4,6])

def testReduce():

    print 'the total is:',reduce((lambda x,y:x+y),range(5))

if __name__ == '__main__':

    print '_'*20

    testFilter()

    testFilterLambda()

    testFilterList()

    testFilterParseList()

    print '_'*20

    testMap()

    testMapMultiList()

    testMapNoneList()

    print '_'*20

    testReduce()

'''

Output:

____________________

[13, 75, 31, 95]

[39, 49, 89, 53, 7]

[25, 77, 95, 79]

[91, 41, 31, 85]

____________________

[2, 3, 4, 5, 6, 7, 8]

[3, 7, 11]

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

____________________

the total is: 10

'''

'Global or Local'

def foo():

    m = 3

    def bar():

        n = 4

        print m + n

    print m

    bar()

#print m

#bar()

foo()

'Example about closure'

def counter(start_at = 0):

    count = [start_at]

    def incr():

        count[0] += 1

        return count[0]

    return incr

count = conter(5) #From this we can see this seems like the object of a class

print count()

print count()