ex37.py

#!/bin/python2
# -*- coding: utf-8 -*-

# ex37: Symbol Review

# and, or, not, if, elif, else

print "#1##############################"

if True and False:
    print "#1 can't be printed"

if False and False:
    print "#2 can't be printed"

if True and True:
    print "#3 can be printed!"

if False or True:
    print "#4 can be printed!"

if True or False:
    print "#5 can be printed!"

if True or No_Matter_What:
    print "#6 can be printed!"

if not(False and No_Matter_What):
    print "#7 can be printed!"

rainy = True
sunny = False
if rainy:
    print "It's rainny today!"
elif sunny:
    print "It's sunny today!"
else:
    print "It's neither rainny nor sunny today!"


# del, try, except, as

print "#2##############################"

x = 10
print x

del x
try:
    print x
except NameError as er:
    print er

    
# from, import

print "#3##############################"

from sys import argv
script = argv
print "The script name is %s " % script

# for, in
for i in range(0, 10):
    print i,

# assert
try:
    assert True, "\nA True!"
    assert False, "\nA false!"
except AssertionError as er:
    print er

# global, def
print "#4##############################"
x = 5

def addone():
    # annouce that x is the global x
    global x
    x += 1

addone()
print "x is %d", x

# finally

print "#4##############################"

import time
try:
    f = open('sample.txt')
    while True: # our usual file-reading idiom
        line = f.readline()
        if len(line) == 0:
            break
        print line 
except KeyboardInterrupt:
    print '!! You cancelled the reading from the file.'
finally:
    f.close()
    print '(Cleaning up: Closed the file)'
    
# with

print "#5##############################"

with open("sample.txt") as f:
    print f.read()

# pass, class

print "#6##############################"

class NoneClass:
    ''' Define an empty class. '''
    pass

empty = NoneClass()
print(empty)

class Droid:
    ''' Define a robot with a name. '''
    def __init__(self, name):
        self.name = name
        print "Robot %s initialized." % self.name
    def __del__(self):
        print "Robot %s destroyed." % self.name
    def sayHi(self):
        print "Hi, I'm %s." % self.name

r2d2 = Droid('R2D2')
r2d2.sayHi()
del r2d2

# exec

print "#7##############################"

print "Here I will use exec function to calculate 5 + 2"
exec("print '5 + 2 = ' , 5 + 2")

# while, break

print "#8##############################"

while True:
    try:
        num = int(raw_input("Let's guess an integer:"))
        if num > 10:
            print "too big!"
        elif num < 10:
            print "too small!"
        else:
            print("Congrats! You will!")
            break
    except ValueError:
        print "Please insert a value!"

# raise

print "#9##############################"

class ShortInputException(Exception):
    ''' A user-defined exception class. '''
    def __init__(self, length, atleast):
        Exception.__init__(self)
        self.length = length
        self.atleast = atleast
try:
    text = raw_input('Enter something long enough --> ')
    if len(text) < 3:
        raise ShortInputException(len(text), 3)
    # Other work can continue as usal here
except EOFError:
    print 'Why did you do an EOF on me?'
except ShortInputException as ex:
    print 'ShortInputException: The input was {0} long, expected at least {1}'\
          .format(ex.length, ex.atleast)    
else:
    print('No exception was raised.')

# yield

print "#10##############################"

print "Now we counter from 1 to 99: "

def make_counter(max):
    x = 1
    while x < max:
        yield x
        x = x + 1

for i in make_counter(100):
    print i,

print "\n\nNow we calculate fibonacci series: "            
    
def fib(max):
    ''' A fibonacci secries generator.

    Calculates fibonacci numbers from 0 to max.
     '''
    a, b = 0, 1
    while a < max:
        yield a
        a, b = b, a+b

for num in fib(100):
    print num,

# lambda

print "\n#11##############################"

def makeDouble():
    ''' double given value '''
    return lambda x:x * 2

adder = makeDouble()
num_list = [5, 10, 15, 'hello']
print '\nNow we multiples each elements in num_list with 2:'
for num in num_list:
    print adder(num)