#acl AdminGroup:read,write EditorGroup:read All:read
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<<TableOfContents(3)>>
= Variable names =
Allowed names for identifier (name of variable or function):
 * Any sequence of alphabetical character, number, or underline character {{{_}}}
 * First symbol has to be a character
 * Case sensitive
 * Not a python built-in keyword

== Name space ==

The Python interpreter maps the name of an identifier in the active name space. The active name space depends on the active code block (module, function). The identifier can be local or global with respect to the active code block.

{{{#!python
def bad_style(x):
	# Name space of bad_style
	global y
	y=x 
	z=x
	return x

# Name space of __main__
x,y,z=2,2,2
x=bad_style(1)
print 'x=',x,'y=',y,'z=',z
# y is changed!
}}}

{{{#!python
import scipy
scipy.pi # pi is in the name space of scipy

from scipy import pi
pi # pi is in the active name space

from scipy import *
pi # all identifiers of scipy are in the active name space

del(pi) # Deletes pi from the active name space
reset   # ipython function to delete all identifiers
}}}
= Built-in =

== Scalar ==
 * Plain integer: {{{9}}}
 * Long integer: {{{9**99, 1L}}}
 * Hex integer: {{{0x10}}}
 * Floating point: {{{0.1}}}
 * Exponential floating point: {{{1e-3}}}
 * Complex: {{{3+2j}}}

=== Casting ===

 * int()
 * long()
 * float()
 * complex()
 * str()

== Sequences ==

=== String ===
{{{#!python
s1='Hello world'
s2="Hello world"
s1==s2

s='"'
s="'"
}}}
== Dictionary ==
{{{#!python
D={1:'one',2:'two','one':1,'two':2}
D['one']
D[1]
}}}

= Extended data types =

== Array ==

NumPy/SciPy provides a multidimensional '''array''' data type. An array can hold arbitrary Python objects but usually they are used for N-dimensional numeric data types.

=== Array creation ===

 * {{{empty((d1,d2),dtype)}}} returns uninitialized array of shape d1,d2. 
 * {{{zeros((d1,d2),dtype)}}} returns array of shape d1,d2 filled with zeros
 * {{{ones((d1,d2),dtype)}}} returns array of shape d1,d2 filled with ones
 * {{{array(object,dtype)}}} returns an array from an object, e.g. a list
 * {{{dtype}}} fundamental C data type e.g. uint8, int16, int64, float32, float64

=== Array indexing ===

 * {{{A[y,x]}}} returns (y,x) element of the array
 * {{{A[:,x]}}} returns all elements of the y-dimension at x
 * {{{A[y1:y2,x]}}} 
 * {{{A[:,:]}}} returns a copy of two dimensional array A 
 * {{{A[:,:,0]}}} returns the first sub-image of a 3-dimensional array