Python

How to install Python ?

For Ubuntu Systems

$ sudo apt-get install python3

$ sudo apt-get install python3-pip

$ sudo apt-get install ipython3

$ sudo apt-get install python3-numpy

For Fedora Systems

$ su # change to root user and run the following commands

# dnf install python3

# dnf install python3-pip

# dnf install python3-numpy

# dnf install python3-ipython

For Windows Systems

users can get the Python3 (Python3.5) from Miniconda (or Anaconda) distribution available at

the url: http://conda.pydata.org/miniconda.html

After installing the distribution, run the following commands in a command window.

> conda update conda

> conda install ipython

> conda install numpy

How to open python prompt after installation?

Step 1: Open Command Prompt

Step 2: Type "python"

Result: It should show python version installed in your system and displays python prompt.

How to close python prompt?

Type exit() to close the python prompt

Python Basics

1.Objects

>>> s="hello"

>>>s.capitalize()

Hello

>>>s.replace("lo","p")

help

2. Basic Types

>>>int(3.2)

3

>>> float(2)

2.0

>>> complex(1)

(1+0j)

>>> (1+2j)*(1-2j) #python can handle complex math

(5+0j)

>>> round(0.8)

1.0

>>> int(round(0.8))

1

3.Calculator

>>> 1+1

2

>>> 8/3

2

>>> 8./3

2.6666666666666665

>>> 8**2 #8 to the power of 2

64

>>> 8**0.5 #Square root of 8

2.8284271247461903

>>> 8 % 3 #modulus operator returns remainder

2

>>> 4 % 3.

1.0

4.Boolean values and comparison operators

>>> 1 > 6

False

>>> 2 <= 2

True

>>> 1 == 2

False

>>> 2 != 5

True

>>> not 2 == 5

True

>>> int(True)

1

>>> 0==False

True

>>> (2 > 1) and (5 < 8)

True

>>> (2 > 1) or (10 < 8)

True

5.Variable Assignment

>>> a = 1

>>> a

1

>>> b = 2

>>> b == a

False

>>> a = 1

>>> a = a + 1

>>> a

2

>>> a += 1

>>> a

3

>>> a -= 3

>>> a

0

6.Strings

>>> s = "molecular simulation"

>>> print s

molecular simulation

>>> "molecular " + 'simulation'

'molecular simulation'

>>> s = "hello"*3

>>> s

'hellohellohello'

>>> len("Scott's class") #To find string length in terms of number of characters

13

>>> "ram" in "Programming is fun."

True

>>> "y" in "facetious"

False

>>> s = "The value of pi is %8.3f." % 3.141591

>>> print s

The value of pi is 3.142

7.Lists

>>> list1= [1,2,3,4,5]

>>> print list1

[1, 2, 3, 4, 5]

>>> [1,2] + [3,4]

[1, 2, 3, 4]

>>> [1,2]*3

[1, 2, 1, 2, 1, 2]

>>> range(4) #range() function lists sequence of numbers. syntax is range(start,stop,step)

[0, 1, 2, 3]

>>> range(1, 4)

[1, 2, 3]

>>> range(0, 8, 2)

[0, 2, 4, 6]

>>> len([1, 3, 5, 7])

4

8. Accessing list elements

>>> l = [1,4,7]

>>> l[0]

1

>>> l[2]

7

>>> l = [1,4,7]

>>> l[0] = 5

>>> l

[5, 4, 7]

>>> l = [1,4,7]

>>> l[-1]

7

>>> l[-3]

1