Python is a high-level, interpreted, open-source programming language that emphasizes readability of source code. In this notebook some of the features of the language as well as key modules in the the Scientific Python ecosystem will be introduced.

Aside using the python shell, Python scrips, and IPython with the "Hello world" example.

Variable Types



In [1]:

    
a = 1   # integers



In [2]:

    
a + 1









    Out[2]:





2



In [3]:

    
b = 2.1  # float
type(b)









    Out[3]:





float



In [4]:

    
c = 1.5 + 0.5j  # complex numbers
print c.real
print c.imag
type(c)









    



1.5
0.5






    Out[4]:





complex



In [5]:

    
d = 3 > 4  # booleans
print d
type(d)









    



False






    Out[5]:





bool



In [6]:

    
a = 1
b = 2.5
a + b









    Out[6]:





3.5



In [7]:

    
# types can be cast
a = 1
print a
print float(a)



In [8]:

    
s = "Hello everyone"   # strings
type(s)









    Out[8]:





str

Containers

Lists



In [9]:

    
# lists
l = ['red', 'blue', 'green', 'black', 'white']
type(l)









    Out[9]:





list



In [10]:

    
len(l)









    Out[10]:





5



In [11]:

    
print l[0]
print l[1]
print l[2]









    



red
blue
green



In [12]:

    
print l[-1]   # last element
print l[-2]









    



white
black



In [13]:

    
print l[2:5]









    



['green', 'black', 'white']



In [14]:

    
print l[2:-1]









    



['green', 'black']



In [16]:

    
l









    Out[16]:





['red', 'blue', 'green', 'black', 'white']



In [15]:

    
print l[1:6:2]









    



['blue', 'black']



In [17]:

    
l[::-1]









    Out[17]:





['white', 'black', 'green', 'blue', 'red']



In [18]:

    
l









    Out[18]:





['red', 'blue', 'green', 'black', 'white']



In [19]:

    
l[0] = 'orange'
print l









    



['orange', 'blue', 'green', 'black', 'white']



In [20]:

    
ll = [5, 22.9, 14.8+1j, 'hello', [1,2,3]]



In [21]:

    
ll









    Out[21]:





[5, 22.9, (14.8+1j), 'hello', [1, 2, 3]]



In [22]:

    
print ll[0]
print ll[1]
print ll[2]
print ll[3]
print ll[4]









    



5
22.9
(14.8+1j)
hello
[1, 2, 3]

Dictionaries



In [23]:

    
d = {'name': 'Jonathan', 'id': 223984, 'location': 'USA'}



In [24]:

    
d.keys()









    Out[24]:





['location', 'name', 'id']



In [25]:

    
d.values()









    Out[25]:





['USA', 'Jonathan', 223984]



In [26]:

    
d['name']









    Out[26]:





'Jonathan'



In [27]:

    
d['id']









    Out[27]:





223984



In [28]:

    
d['id'] = 1234



In [29]:

    
d['id']









    Out[29]:





1234

Tuples



In [30]:

    
t = ('red', 'blue', 'green')



In [31]:

    
t[0]









    Out[31]:





'red'



In [32]:

    
t[1:3]









    Out[32]:





('blue', 'green')



In [33]:

    
t[1] = 'orange'









    



---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-33-fbab64ebbc9d> in <module>()
----> 1 t[1] = 'orange'

TypeError: 'tuple' object does not support item assignment

Flow control



In [34]:

    
a = 10
if a == 10:
    print "a is 10"
# if, elif, else



In [38]:

    
a = 10
if a > 10:
    print "a is larger than 10"
else:
    print "a is less than 10... or maybe equal too"









    



a is less than 10... or maybe equal too



In [41]:

    
a = 4
if a > 10:
    print "a is larger than 10"
elif a < 10:
    print "a is less than 10"
else:
    print "a is equal to 10"









    



a is less than 10



In [42]:

    
for i in range(10):
    print i



In [43]:

    
for color in ['red', 'blue', 'orange']:
    print "My favorite color is", color









    



My favorite color is red
My favorite color is blue
My favorite color is orange



In [44]:

    
# list comprehensions
[i*2 for i in range(10)]









    Out[44]:





[0, 2, 4, 6, 8, 10, 12, 14, 16, 18]

Functions



In [45]:

    
def func():
    print "Hello world"



In [46]:

    
func()









    



Hello world



In [47]:

    
def func2(name):
    print "Hello", name



In [48]:

    
func2("Jonathan")









    



Hello Jonathan



In [49]:

    
def times2(x):
    return x * 2



In [50]:

    
y = times2(2)
print y



In [51]:

    
def times_something(x, y=2):
    print x*y



In [52]:

    
times_something(3)



In [53]:

    
times_something(3, 3)



In [54]:

    
w = times_something



In [55]:

    
w(3, 3)



In [56]:

    
f_list = [times_something, times2]



In [57]:

    
f_list[1](9)









    Out[57]:





18

Classes



In [58]:

    
class Car(object):
    
    engine = 'V4'    # class attribute
    
    def start(self):  # class method
        print "Starting the car with a", self.engine, "engine"



In [ ]:

    
class SuperCar(Car):



In [59]:

    
mycar = Car()



In [60]:

    
type(mycar)









    Out[60]:





__main__.Car



In [61]:

    
mycar.engine









    Out[61]:





'V4'



In [64]:

    
mycar.start()









    



Starting the car with a V4 engine



In [65]:

    
mycar.engine = 'V6'



In [66]:

    
mycar.engine









    Out[66]:





'V6'



In [67]:

    
mycar.start()









    



Starting the car with a V6 engine

The Scientific Python stack

NumPy



In [68]:

    
import numpy as np



In [76]:

    
a = np.array([0, 1, 2, 3, 4, 5, 6, 7])

a



In [71]:

    
a.shape









    Out[71]:





(4,)



In [72]:

    
a.ndim









    Out[72]:





1



In [73]:

    
a.dtype









    Out[73]:





dtype('int64')



In [78]:

    
a[0::2]









    Out[78]:





array([0, 2, 4, 6])



In [80]:

    
a[a>3]









    Out[80]:





array([4, 5, 6, 7])



In [83]:

    
a * 2 + 100









    Out[83]:





array([100, 102, 104, 106, 108, 110, 112, 114])



In [86]:

    
a.









    Out[86]:





3.5



In [87]:

    
b = np.arange(12).reshape(3,4)



In [88]:

    
b.shape









    Out[88]:





(3, 4)



In [ ]:

    
b



In [ ]:

    
b[1,2]



In [ ]:

    
b[0:2, ::-1]

SciPy

matplotlib



In [92]:

    
%pylab inline









    



Populating the interactive namespace from numpy and matplotlib



In [93]:

    
plot([1,2,3])









    Out[93]:





[<matplotlib.lines.Line2D at 0x1083f0090>]



In [94]:

    
a = np.random.rand(30, 30)
imshow(a)
colorbar()









    Out[94]:





<matplotlib.colorbar.Colorbar instance at 0x1085b6c20>



In [97]:

    
import matplotlib.pyplot as plt



In [ ]: