[08/31/2011]

Programming languages:
C++ - 100
Java - 75
C - 65
Python - 20
Perl - 8
C# - 10
PHP - 24
Ruby - 6
HTML/CSS/JavaScript - 40

Python -- What's the big deal?

 a scripting language?

 #!/usr/local/bin/python


 Python -- OO stuff is optional

 Design goals: easy to read, easy to learn, easy to maintain

 known as a productive language -- rapid prototyping



 Python is an interpreter


 compilation:

              g++
 C++ source  =====>  Object code (.o) =======> executable (native code)


              javac
 Java source =======> Byte Code (.class) ======> Java Virtual Machine
                                                     (JVM)

          PORTABILITY

 Python source  ======> Byte code (.pyc) ========> Python Virtual Machine
     (.py)                                              (PVM)



 TO DO: download and install.....

  http://python.org/getit/    <==== download 3.x (latest stable)


 Advantages: free
             garbage collection
             functional programming (list processing)
             self-documenting

 Disadvantages: slower
          (but can mix Python with compiled C, C++ code, etc.)

 Python at times is also considered "glue code"




 C++, Java, C ---- the "int" data type

       32-bit int range -2,147,483,648 to 2,147,483,647

 Python has no limit on range of integers (see below)





 Every variable in Python is simply a reference variable (or pointer)

 cost = 15.99

                      +---------+
  cost =============> |  15.99  |
                      +---------+


 cost = 18.99

                      +---------+
                      |  15.99  | (garbage)
                      +---------+

                      +---------+
  cost =============> |  18.99  |
                      +---------+








Below is copy-and-paste of most of a python session on a Linux box
 (note this is v2.5 of Python, so the division operator is different than 3.x)

>>> 9.8 * 6
58.800000000000004
>>> 9.8 / 4.2
2.3333333333333335
>>> 9.8 // 4.2
2.0
>>> 9.8 % 4.2
1.4000000000000004
>>> 5 ** 1000
933263618503218878990089544723817169617091446371708024621714339795966910975775634454440327097881102359594989930324242624215487521354032394841520817203930756234410666138325150273995075985901831511100490796265113118240512514795933790805178271125415103810698378854426481119469814228660959222017662910442798456169448887147466528006328368452647429261829862165202793195289493607117850663668741065439805530718136320599844826041954101213229629869502194514609904214608668361244792952034826864617657926916047420065936389041737895822118365078045556628444273925387517127854796781556346403714877681766899855392069265439424008711973674701749862626690747296762535803929376233833981046927874558605253696441650390625L
>>> 5.0 ** 1000
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
OverflowError: (34, 'Numerical result out of range')
>>> 1/3
0
>>> 10/3
3
>>> 100/3
33
>>> 1j
1j
>>> 8j * 8j
(-64+0j)
>>> import math
>>> math.pi
3.1415926535897931
>>> math.e
2.7182818284590451
>>> math.sqrt( 87 )
9.3273790530888157
>>> math.factorial( 3 )
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
AttributeError: 'module' object has no attribute 'factorial'
>>> math.fact( 3 )
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
AttributeError: 'module' object has no attribute 'fact'
>>> dir(math)
['__doc__', '__file__', '__name__', 'acos', 'asin', 'atan', 'atan2',
'ceil', 'cos', 'cosh', 'degrees', 'e', 'exp', 'fabs', 'floor', 'fmod',
'frexp', 'hypot', 'ldexp', 'log', 'log10', 'modf', 'pi', 'pow',
'radians', 'sin', 'sinh', 'sqrt', 'tan', 'tanh']
>>> help( math.floor )
Help on built-in function floor in module math:

floor(...)
   floor(x)

   Return the floor of x as a float.
   This is the largest integral value <= x.

>>> help( math.hypot )
Help on built-in function hypot in module math:

hypot(...)
   hypot(x,y)

   Return the Euclidean distance, sqrt(x*x + y*y).

>>>
>>> dir( __builtins__ )
['ArithmeticError', 'AssertionError', 'AttributeError',
'BaseException', 'DeprecationWarning', 'EOFError', 'Ellipsis',
'EnvironmentError', 'Exception', 'False', 'FloatingPointError',
'FutureWarning', 'GeneratorExit', 'IOError', 'ImportError',
'ImportWarning', 'IndentationError', 'IndexError', 'KeyError',
'KeyboardInterrupt', 'LookupError', 'MemoryError', 'NameError',
'None', 'NotImplemented', 'NotImplementedError', 'OSError',
'OverflowError', 'PendingDeprecationWarning', 'ReferenceError',
'RuntimeError', 'RuntimeWarning', 'StandardError', 'StopIteration',
'SyntaxError', 'SyntaxWarning', 'SystemError', 'SystemExit',
'TabError', 'True', 'TypeError', 'UnboundLocalError',
'UnicodeDecodeError', 'UnicodeEncodeError', 'UnicodeError',
'UnicodeTranslateError', 'UnicodeWarning', 'UserWarning',
'ValueError', 'Warning', 'ZeroDivisionError', '_', '__debug__',
'__doc__', '__import__', '__name__', 'abs', 'all', 'any', 'apply',
'basestring', 'bool', 'buffer', 'callable', 'chr', 'classmethod',
'cmp', 'coerce', 'compile', 'complex', 'copyright', 'credits',
'delattr', 'dict', 'dir', 'divmod', 'enumerate', 'eval', 'execfile',
'exit', 'file', 'filter', 'float', 'frozenset', 'getattr', 'globals',
'hasattr', 'hash', 'help', 'hex', 'id', 'input', 'int', 'intern',
'isinstance', 'issubclass', 'iter', 'len', 'license', 'list',
'locals', 'long', 'map', 'max', 'min', 'object', 'oct', 'open', 'ord',
'pow', 'property', 'quit', 'range', 'raw_input', 'reduce', 'reload',
'repr', 'reversed', 'round', 'set', 'setattr', 'slice', 'sorted',
'staticmethod', 'str', 'sum', 'super', 'tuple', 'type', 'unichr',
'unicode', 'vars', 'xrange', 'zip']
>>>
>>> float( 3 )
3.0
>>> help( pow )
Help on built-in function pow in module __builtin__:

pow(...)
   pow(x, y[, z]) -> number

   With two arguments, equivalent to x**y.  With three arguments,
   equivalent to (x**y) % z, but may be more efficient (e.g. for longs).

>>> int( 4.56 )
4
>>> round( 4.56 )
5.0
>>> int( 18.64 )
18
>>> round( 18.64, 2 )
18.640000000000001
>>> round( 18.64, 1 )
18.600000000000001
>>> 20 * 30.5
610.0
>>> 'http://'
'http://'
>>> "http://"
'http://'
>>> 'she said, "no way!"'
'she said, "no way!"'
>>> "what's up doc"
"what's up doc"
>>> """
... ab"cd
... ef'gh
... """
'\nab"cd\nef\'gh\n'
>>>
>>> len( 'abcd' )
4
>>> len( '' )
0
>>> 5 + len( 'abcd' )
9
>>> 'hot' + 'dog'
'hotdog'
>>> 'hot' * 2 + 'dog'
'hothotdog'
>>> 10 * 'hee'
'heeheeheeheeheeheeheeheeheehee'
>>> 3 * 'ha' + 'ho' * 3
'hahahahohoho'
>>> float( '3.14' )
3.1400000000000001
>>> int( '500' )
500
>>> int( '500' * 3 )
500500500
>>>
>>> str( -9.876 )
'-9.876'
>>>
>>> 'cost is $' + 15.99 * 1.08
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
TypeError: cannot concatenate 'str' and 'float' objects
>>> 'cost is $' + str( 15.99 * 1.08 )
'cost is $17.2692'
>>> 'cost is $' + str( round( 15.99 * 1.08 ) )
'cost is $17.0'
>>> 'cost is $' + str( round( 15.99 * 1.08 ), 2 )
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
TypeError: str() takes at most 1 argument (2 given)
>>> 'cost is $' + str( round( 15.99 * 1.08, 2 ) )
'cost is $17.27'
>>> cost = 15.99 * 1.08
>>> cost
17.269200000000001
>>> round( cost, 2 )
17.27
>>> cost
17.269200000000001
>>> cost = round( cost, 2 )
>>> cost
17.27
>>>
>>> cost = 'too much'
>>> cost
'too much'
>>> lumberjack = 'okay'
>>> lumberjack
'okay'
>>> lumberjack.capitalize()
'Okay'
>>> lumberjack.center( 40 )
'                  okay                  '
>>> lumberjack
'okay'
>>> lumberjack.lower()
'okay'
>>> lumberjack.upper()
'OKAY'
>>> lumberjack.islower()
True
>>> name = 'david eric goldschmidt'
>>> name.capitalize()
'David eric goldschmidt'
>>> name.title()
'David Eric Goldschmidt'
>>>
>>> x, y, z = 5, 3.14, 'pi'
>>> x
5
>>> y
3.1400000000000001
>>> z
'pi'
>>> x, y = y, x
>>> x
3.1400000000000001
>>> y
5
>>>
>>> radius = input( 'Enter radius: ' )
Enter radius: 5.67
>>> radius
5.6699999999999999
>>> quit()