''' Variables '''

# Python provides dynamic typing of its variables.
# You do not have to define a type of the variable. Python will take care of this for you.

# This is a text
s = "abc"
s = 'abc'

# This is an integer
x = 1
y = 2
z = x + y

''' Loops and if clauses '''

# The body of the loops and if clauses is indented.
# Each line within a block must be indented by the same amount

x = int(raw_input("Please enter an integer: ")) # input
if x < 0:
    x = 0
    print 'Negative changed to zero' # output
elif x == 0:
    print 'Zero'
elif x == 1:
    print 'Single'
else:
    print 'More'

a, b = 0, 1 # multiple assignment
while b < 10:
    print b
    a, b = b, a+b

a = ['cat', 'window', 'defenestrate']
for x in a:
    print x, len(x)

''' Methods '''

# Python allows to define methods via the keyword def.
# As the language is interpreted, the methods need to be defined before using it.

def add(a, b):
    return a + b

print add(1, 2)

''' Lists '''

# List items need not all have the same type.
A = ['a', "b", 123]

# List Comprehensions
S = [x**2 for x in range(10)] # [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
V = [2**i for i in range(13)] # [1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096]
M = [x for x in S if x % 2 == 0] # [0, 4, 16, 36, 64]

# Print the first list element
print(A[0]) # List indices start at 0

# Print the last element
print(A[-1]) # Negative values starts the list from the end

# Sublist
print(A[0:2]) # first and second element

# Add elements to the list
A.append("x")

# Print the content of the list
for element in A:
    print(element)
# or
a = ['Mary', 'had', 'a', 'little', 'lamb']
for i in range(len(a)): # range(10) generates a list of 10 values (0, 1, ..., 9)
    print a[i]

''' break and continue Statements, and else Clauses on Loops '''

# The break statement, like in C, breaks out of the smallest enclosing for or while loop.

# The continue statement, also borrowed from C, continues with the next iteration of the loop.

# Loop statements may have an else clause;
# it is executed when the loop terminates through exhaustion of the list (with for)
# or when the condition becomes false (with while),
# but not when the loop is terminated by a break statement.
for n in range(2, 10):
    for x in range(2, n): # range(2, n): 2, 3, ..., n-1
        if n % x == 0:
            print n, 'equals', x, '*', n/x
            break
    else: # loop fell through without finding a factor
        print n, 'is a prime number'

''' The range() Function '''

range(10) # [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

# It is possible to let the range start at another number,
# or to specify a different increment (even negative)
range(5, 10) # [5, 6, 7, 8, 9]
range(0, 10, 3) # [0, 3, 6, 9]
range(-10, -100, -30) # [-10, -40, -70]

''' The timeit() Function '''

# The timeit() function runs the code many times (default one million)
# and takes an average of the timings

import timeit

def function(x):
    return x

# no import needed if the method is a Python built-in function
t = timeit.Timer('function(123)', 'from __main__ import function')

# time function 1000 times, divide result by 1000
# then multiply by 1000000 to get microseconds
# measuredTime = (1000000 * t.timeit(number=1000)/1000) = (1000 * t.timeit(number=1000))
measuredTime = (1000 * t.timeit(number=1000))

print "function(123) takes %0.3f micro-seconds" % measuredTime