Page 3 - Tips, tricks, inspiration, etc

#!/usr/bin/env python

import sys

sys.stdout = file('/Users/User/Documents/example.txt', 'w')

...

import time

def print_timing(func):
    def wrapper(*arg):
        t1 = time.clock()
        res = func(*arg)
        t2 = time.clock()
        print '%s took %sms.' % (func.func_name, (t2-t1)*1000.)
        return res
    return wrapper

@print_timing        
def f1():
    x=[]
    for i in xrange(1,10000):
        x.append(str(i))
    s = ''.join(x)

@print_timing
def f2():
    x=''
    for i in xrange(1, 10000):
        x += str(i)

if __name__ == '__main__':
    f1()
    f2()

class Foo:
  def __init__(self, integer=0):
    if not isinstance(integer, int):
      try:
        integer = int(integer)
      except: raise
    self.i = integer
  def __add__(self, other): # new = self + other
    new = self.__class__() # 1. Create
    if isinstance(other, self.__class__): # 2. Check
      new.i = other.i
    else: raise ValueError("foo+other: Incompatible type addition (got %s, expected %s)" % (other, self.__class__.__name__))
    return new # 3. Return
  def __iadd__(self, other): self += other
    if  isinstance(other, self.__class__):
      self.i = other.i
      return self
    else:
      raise ValueError("foo+=other: Incompatible type addition (got %s, expected %s)" % (other, self.__class__.__name__))

print '%s took %sms.' % (func.func_name, (t2-t1)*1000.)

print '%s took %0.3fms.' % (func.func_name, (t2-t1)*1000.)

Python 2.4.1 (#1, May 27 2005, 18:02:40)
[GCC 3.3.3 (cygwin special)] on cygwin
Type "help", "copyright", "credits" or "license" for more information.
>>> print '-%s-' % 123
-123-
>>> print '-%s-' % 'hello'
-hello-
>>> print '-%s-' % 123.456
-123.456-
>>> print '-%r-' % 'hello'
-'hello'-
>>> print '-%s-' % Exception
-exceptions.Exception-
>>> print '-%r-' % Exception
-<class exceptions.Exception at 0x46526c>-
>>>

Original - python Code d = path(os.environ['HOME']) for f in d.walkfiles('*~'): f.remove()

d = path(os.environ['HOME'])
for f in d.walkfiles('*~'):
    f.remove() 

# input() actually uses raw_input() and then tries to
# convert the input data to a number using eval()
# this leads to some unexpected results

x = 123
a = input('Enter x: ')
# if the user enters the character x instead of a value then a = 123, try it
print a

b = input('Enter 355/113.0 : ')
# eval() will give b the result of the math expression, can be useful
print b

# this would be the more dangerous side of input() and its hidden partner eval()
# eval() evaluates this statement and executes it
# and will actually create a new directory on your C drive, somewhat harmless
# but a troublemaker could enter a similar statement to wipe out files!!!!
z = input("Enter  __import__('os').mkdir('C:/Aatest')  : ")

c = input('Enter "Hello" : ')
# since "Hello" is a string it will be passed on to c (who needs raw_input()?)
print c, type(c)

d = input('Enter a list like [1,2,3] : ')
# you guessed it, d will be a list, can be useful
print d, type(d)

# this will give an error since eval() doesn't know what to do with just enter
z = input('Press Enter ...')

Original - python Code z = input("Enter __import__('os').mkdir('C:/Aatest') : ")

z = input("Enter  __import__('os').mkdir('C:/Aatest')  : ") 

[x for x in iterable if x]

def foo():
  #do stuff

def foo2():
  #do stuff

def foo3():
  #do stuff

x = {value1 : foo,
       value2 : foo2,
       value3 : foo3,}

x[some_variable]()

# an improved switch/case like statement to replace
# multiple if/elif/else statements

def switch_case(case):
    return "You entered " + {
    '1' : "one",
    '2' : "two",
    '3' : "three"
    }.get(case, "a bad number")

num = raw_input("Input a number between 1 and 3: ")
print switch_case(num)