In python there are two modes available to program as Matlab:
- Interactive Mode Programming
- Script Mode Programming
Now let’s see how to program in these modes:
Interactive Mode Programming
Python instructions can be directly executed from the python prompt.
Ex:
Python 3.6.0a3 (v3.6.0a3:f3edf13dc339, Jul 11 2016, 21:40:24) [MSC v.1900 64 bit (AMD64)] on win32 Type "copyright", "credits" or "license()" for more information. >>>print("Hello world!") Hello world!
Ex:

Fig.1: Interactive Mode Programming example#1
>>>x=2 >>>print(x) 2 >>>
Script Mode Programming
Similar to m file in matlab, python also provides facility to write program in a script file with .py extension.
Lets write our first script file in python to print “Hello world!”:
You can write your code in a notepad file and save it with extension .py as:

Fig.3: Script mode programming with notepad

Fig.5:Run script from command prompt.
OR
you can open python code editor from IDLE (python) as:

Fig.4: Script mode programming with IDLE

Fig.6: Run script from IDLE
Python Identifiers
A Python identifier is a name used to identify a variable, function, class, module or other object.
Rules for Identifiers:
- An identifier starts with a letter A to Z or a to z or an underscore (_)
- It contains letters, underscores and digits (0 to 9) only
- Python is a case sensitive programming language
- Class names start with an uppercase letter
- All other identifiers start with a lowercase letter
- Private identifiers start with (_) underscore
- Strongly private identifiers start with (__) double underscore
- A language-defined special name identifier is defined by adding two trailing underscores
Python Reserved Words
- Reserved words cannot be used as constant or variable or any other identifier names
- Python keywords contain lowercase letters only
Following are the reserved words in python:
and | exec | not |
assert | finally | or |
break | for | pass |
class | from | |
continue | global | raise |
def | if | return |
del | import | try |
elif | in | while |
else | is | with |
except | lambda | yield |
Blocks of code
- Unlike C, C++ and Java, in python blocks are not defined with ({ }) set of curly braces
- Instead it uses line indentation to indicate blocks of code for class and function definitions or flow control
- All statements of a block must be indented the same amount. The number of spaces in the indentation can be variable
Ex:
x=0 while(x<2): print(x) x=x+1 print("Finally x=", x)
OUTPUT
0 1 Finally x= 2

Fig.7: Indents in Python example
x=0 while(x<2): print(x) x=x+1 print("Finally x=", x)
Here last statement “print” does not belong to any indentation, leads to error.

Fig.8: Wrong indentation
Multi-Line Statements
- In python (\) forward slash is used as line continuous character.
>>> x=2\ +2+\ 3 >>>x 7
It is equivalent to x=2+2+3
- Statements contained within brackets [], {}, or () do not need to use the line continuation character.
>>> x= [2,3 ,4] >>> x [2, 3, 4]
x is an array.
String Literals
To denote string literals in python, single (‘), double (“) and triple (”’ or “””) quotes could be used.
Ex:text='Hey' text1="Hey" text2='''Hey''' text3="""Hey"""
Comments in Python
A hash sign (#) is can be used in python to begins a comment.
# First comment print("Hello word!") # second comment
OUTPUT:
Hello word!
User Input in Python at Run Time
- raw_input() could be used to take user input at run time
- raw_input() prints the arguments passed into it
- raw_input() returns the value entered by the user
Ex:
x=raw_input("Enter some value: ") print x
OUTPUT:
Enter some value: <34> 34
Say, user entered 34, so x=34 and raw_input prints Enter some value:
Multiple Statements in Single Line
Multiple statements separated by semicolon (;) can be written in single line.
Ex:
x = 'foo'; print x, '\n'
OUTPUT:
foo
Suites in Python
Suite in Python is a group of individual statements, which make a block of code. Compound or complex statements, such as if, while, def, and class require a header line and a suite.
Header lines begin the statement (with the keyword i.e. if, while, def, and class) and terminate with a colon (:) and are followed by one or more lines of code, which forms the suite.
Ex:
while expression : statements statements if expression : statements statements elif expression : statements statements else : statements statements
Command line Arguments
Similar to gcc command line arguments, python also provides facility of command line arguments.
- len(sys.argv) gives he number of command-line arguments
- sys.argv gives the list of command-line arguments
- sys.argv[0] is the program i.e. script name
Ex:
import sys print('Number of arguments:', len(sys.argv), 'arguments') print('Argument List:', str(sys.argv))
Run the program from command prompt as python xyz.py argument1 argument2 argument3
OUTPUT:
Number of arguments: 4 arguments Argument List: ['xyz.py', 'argument1', 'argument2', 'argument3']