In [1]:

    

type(4/2) # float


    

    
Out[1]:





float

In [2]:

    

type(4//2) # int, double slash performs integer division


    

    
Out[2]:





int

In [3]:

    

# printf-like syntax
# """ allows printed statements in multiple lines

print("""
Compact decimal notation: %g 
Compact scientific notation: %e
Percent sign: %.2f%%
""" % (1234.5678, 1234.5678, 1234.5678))


    

    




Compact decimal notation: 1234.57 
Compact scientific notation: 1.234568e+03
Percent sign: 1234.57%

In [4]:

    

# format string syntax

print("""
Compact decimal notation: {dec_:g}
Compact scientific notation: {exp_:e}
Percent sign: {per_:.2f}%
""".format(dec_=1234.5678, exp_=1234.5678, per_=1234.5678))


    

    




Compact decimal notation: 1234.57
Compact scientific notation: 1.234568e+03
Percent sign: 1234.57%

In [5]:

    

from sympy import (
    symbols,    # define symbols
    diff,       # derivatives
    integrate,  # integrals
    lambdify,   # symbolic expression -> python function
    latex,      # create latex expressions
    sin         # symbolic sine function
)

x = symbols('x')
y = sin(x)


    

In [6]:

    

dydx = diff(y, x)
dydx


    

    
Out[6]:





cos(x)

In [7]:

    

integrate(dydx)


    

    
Out[7]:





sin(x)

In [8]:

    

f = lambdify(x, y)


    

In [9]:

    

from math import pi
f(pi/2)


    

    
Out[9]:





1.0

In [10]:

    

y.series(x, 0, 6)


    

    
Out[10]:





x - x**3/6 + x**5/120 + O(x**6)

In [11]:

    

print(latex(y.series(x, 0, 6)))


    

    




x - \frac{x^{3}}{6} + \frac{x^{5}}{120} + \mathcal{O}\left(x^{6}\right)

In [12]:

    

from IPython.display import display, Math
display(Math(latex(y.series(x, 0, 6))))


    

    






$$x - \frac{x^{3}}{6} + \frac{x^{5}}{120} + \mathcal{O}\left(x^{6}\right)$$

In [13]:

    

list1 = ['a', 'b', 'c', 'd', 'e']
list2 = [1, 2, 3, 4, 5]

def f(list1, list2):
    
    """ Uses zip to process 2 lists in parallel.
    
    Args:
        list1: first list.
        list2: second list.
    
    """
    
    for i, j in zip(list1, list2):
        print(i, j)


    

In [14]:

    

print(f.__doc__)


    

    




 Uses zip to process 2 lists in parallel.
    
    Args:
        list1: first list.
        list2: second list.
    
    

In [15]:

    

f(list1, list2)


    

    




a 1
b 2
c 3
d 4
e 5

In [16]:

    

import timeit
n = 10000000
list3 = [0]*n
list4 = []
print(timeit.timeit('for i in range(0, n): list3[i] = i', number=1, setup='from __main__ import n, list3'))
print(timeit.timeit('for i in range(0, n): list4.append(i)', number=1, setup='from __main__ import n, list4'))


    

    




0.5182436349568889
0.7834440469741821

In [17]:

    

# '!' executes OS commands 
# installs memory profiler package 
# stores a short script to a file, biglist.py
# executes biglist.py with the memory_profiler module ... slow!
! pip install memory_profiler 
! printf "@profile\ndef biglist():\n list_ = []\n for i in range(0, 1000000):\n  list_.append(i)\n return list_\nbiglist()" > biglist.py
! python -m memory_profiler 'biglist.py'


    

    




Requirement already satisfied: memory_profiler in /Users/phall/anaconda/lib/python3.5/site-packages
Filename: biglist.py

Line #    Mem usage    Increment   Line Contents
================================================
     1   32.344 MiB    0.000 MiB   @profile
     2                             def biglist():
     3   32.344 MiB    0.000 MiB    list_ = []
     4   63.934 MiB   31.590 MiB    for i in range(0, 1000000):
     5   63.934 MiB    0.000 MiB     list_.append(i)
     6   63.688 MiB   -0.246 MiB    return list_

In [18]:

    

# use the **kwargs variable to pass in any number of 
# keyword arguments to a function
def f(**kwargs):
    
    # kwargs is a dict
    if kwargs is not None:
        for key, val in sorted(kwargs.items()):
            print('%s = %s' %(key, val))
            
    print('----------')
        
f(a='hello')
f(a='hello', b='world')
f(a='goodbye', b='cruel', c='world')


    

    




a = hello
----------
a = hello
b = world
----------
a = goodbye
b = cruel
c = world
----------

In [19]:

    

# import numeric sine function
from math import sin
print(sin(0))

# simple function for numerical derivative of f at x
def num_dfdx(f, x, h):
    
    return (f(x + h) - f(x))/float(h)

print(num_dfdx(sin, 0, 0.01))
print(num_dfdx(sin, 0, 1e-6))


    

    




0.0
0.9999833334166665
0.9999999999998334

In [20]:

    

# value1 if condition else value2
def magnitude(x):
    
    # value1 if condition else value2
    return 'small' if 1 >= x >= -1 else 'big'

print(magnitude(0.5))
print(magnitude(-10))


    

    




small
big

In [21]:

    

num_dfdx(lambda x: x**2, 1, 1e-6)


    

    
Out[21]:





2.0000009999243673

In [22]:

    

magnitude = lambda x: 'small' if 1 >= x >= -1 else 'big'
print(magnitude(0.5))


    

    




small

In [23]:

    

# map and lamba used often to apply a simple function
# to all elements in a list
list(map(lambda x: x**2, range(0,10)))


    

    
Out[23]:





[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

In [24]:

    

operator = input('Please type an arithmatic operator: +, -, *, /. ') # read input from command line
print('1 ' + operator + ' 2')                                        # this is a string
print(eval('1 ' + operator + ' 2'))                                  # this evaluates the string as a code expression
print(type(eval('1 ' + operator + ' 2')))                            # this returns the type of the evaluated code expression


    

    




Please type an arithmatic operator: +, -, *, /. /
1 / 2
0.5
<class 'float'>

In [25]:

    

operator = input('Please type an arithmatic operator: +, -, *, /. ') # read input from command line

# define a function - more complex than a simple expression - as string with substitution 
code = """                                                           
def combine():
    x = 1 %s 2
    return x
""" % (operator)
print(code)             # this is a string                                                                         
print(type(exec(code))) # this interprets the function and prints its type, i.e. None
print(combine())        # print output of interpreted function


    

    




Please type an arithmatic operator: +, -, *, /. -
                                                           
def combine():
    x = 1 - 2
    return x

<class 'NoneType'>
-1