# this is the first comment
SPAM = 1	# and this is the second comment
		# ... and now a third!
SPRINT = "# This is not a comment."



2+2
(50-5*6)/4
7/3
7/-3



width = 20
height = 5*9
width * height



x = y = z = 0
x
y
z
x, y, z



3 * 3.75 / 1.5
7.0 / 2



1j * 1J
1j * complex(0,1)
3 - 1j*3
(3 - 1j)*3
(1+2j)/(1+1j)

a=1.5+0.5j
a.real
a.imag

a = 3.0 + 4.0j
float(a)
a.real
a.imag
abs(a)	# sqrt(a.real**2 + a.imag**2)


# in interactive mode, the last printed expression is assigned to the variable, _
tax = 12.5 / 100
price = 100.50
price * tax
_
price + _
round(_, 2)



======
STRING
======

'spam eggs'
'doesn\'t'
"doesn't"
'"Yes," he said.'
"\"Yes,\" he said."
'"Isn\'t, " she said.'

hello = "This is a rather long string containing\n\
several lines of text just as you would do in C.\n\
    Note that whitespace at the beginning of the line is\
 significant."

print hello


hello = r"This is a rather long string containing\n\
several lines of text just as you would do in C."

print hello


print """
Usage: thingy [OPTIONS]
    -h			Display this usage message
    -H hostname		Hostname to connect to
"""



word = 'Help' + 'A'
word
'<' + word * 5 + '>'


'str' 'ing'
'str'.strip() + 'ing'

'str'.strip() 'ing'	# <- This is invalid

word[4]
word[0:2]
word[2:4]
word[:2]
word[2:]
word[:2] + word[2:]
word[:]
word

word[0] = 'x'	# <- Python strings cannot be changed

'x' + word[1:]
'Splat' + word[4]

word[1:100]
word[10:]
word[2:1]

word[-1]	# The last character
word[-2]	# The last-but-one character
word[-2:]	# The lqast two characters
word[:-2]	# Everything except the last two characters
word[-0]
word[0]

word[-10]	# <- string index out of range




====
LIST
====

a = ['spam', 'eggs', 100, 1234]
a
a[0]
a[3]
a[-2]
a[1:-1]

a[:2] + ['bacon', 2*2]
3*a[:3] + ['Boo!']

a
a[2] = a[2] + 23	# <- Unlike strings, wihci are immutable, it is possible to change individual elements of a list

# replace some items
a[0:2] = [1, 12]
a

# remove some
a[0:2] = []
a

# insert some
a[1:1] = ['bletch', 'xyzzy']

# insert (a copy of ) itself a the beginning
a[:0] = a
a

# clear the list: replace all items with an empty list
a[:] = []
a