In Python, there are two types of comments--one is a single-line comment and the other is multiline comment. For a single-line comment, # is used, while for a multiline comment, triple quotes """ are used:

#This is a single line comment in Python

print "Hello World" #This is a single comment in Python

""" For multi-line
comment use three
double quotes
...
"""
print "Hello World!"

Python doesn't care if you use single quotes or double quotes to print a single statement. But, surely, both has some significance while printing complex statements, which we will see soon.

print "Hello World!" and print 'Hello World!' will give the same output Hello World! two times:

How will you print something like this:

I am mad in love  do you think  I am doing the right thing? One way is to enclose the complete thing within the triple quotes as shown here:

print '''I am mad in love
                     do you think
                                 I am doing
                                           the right thing '''

Alternatively, you can also use double quotes three times to achieve the same thing:

print """I am mad in love
                     do you think
                                 I am doing
                                                                                                                             the right thing """

Let's try another example. What should be the outcome of the following statement?

print 'Hey there it's a cow'

The preceding piece of code gives the following results:

C:pydev>python hello.py
File "hello.py", line 1
print 'Hey there it's a cow'
^
SyntaxError: invalid syntax

Python simply interprets that the statement terminated with a single quote after it. The solution is to enclose the complete sentence within double quotes as shown:

print "Hey there it's a cow"

Adding double quotes (") gives an error-free output as shown:

C:pydev>python hello.py
Hey there it's a cow

The Python back slash is used for continuation of the print statement. You can stretch a single statement across multiple lines:

print "Hello
  world "

This gives the following output:

C:pydev>python hello.py
Hello world

For printing a string, either a pair of single (' ') quotes or pair of double quotes (" ") can be used as shown in the succeeding examples: 

print "Hello World 'Mr' Bond"
print 'old world "but" still good'

This gives the following results:

C:pydev>python hello.py
Hello World 'Mr' Bond
old world "but" still good

The escape sequence is used to insert the tab, the newline, the backspace, and other special characters into your code. They give you greater control and flexibility to format your statements and code:

print 'a' 
print 'tHermit' 
print "i know , they are 'great'"

The output is as follows:

C:pydev>python hello.py
Hermit
i know , they are 'great'

The preceding code executes with a beep sound. If you did not hear the beep sound, check your speakers.

Two strings can be joined using the + operator:

print "Only way to join" + "two strings"

The following is the output of the preceding code:

C:pydev>python string_concatenation.py
Only way to join two strings

Consider an example where you would want to print the name, marks, and the age of the person:

print "Name", "Marks", "Age" 
print "John Doe", 80.67, "27" 
print "Bhaskar", 76.908, "27"
print "Mohit", 56.98, "25" 

The output will be as follows:

C:pydev>python hello.py
Name Marks Age
John Doe 80.67 27
Bhaskar 76.908 27
Mohit 56.98 25

You can see the output, but the output that is displayed is not formatted. Python allows you to set the formatted output. If you have done some coding in C language, then you should be familiar with %d, %f, %s. In order to represent an integer %d is used, %f is used for float, and %s is used for string. If you used %5d, it means 5 spaces. If you used %5.2f, it means 5 spaces and .2 means precision. The decimal part of the number or the precision is set to 2. Let's use the formatting on the preceding example:

print "Name Marks Age" 
print ( "%s %14.2f %11d" % ("John Doe", 80.67, 27)) 
print ( "%s %12.2f %11d" %("Bhaskar" ,76.901, 27))
print ( "%s %3.2f %11d" %("Mohit", 56.98, 25)) 

The output we get is as follows:

C:pydev>python hello.py
Name Marks Age
John Doe 80.67 27
Bhaskar 76.90 27
Mohit 56.98 25

The preceding output is much better than the previous one. You can see Marks76.901 set to 76.90 automatically.

The most unique characteristic of Python, unlike other programming languages, is indentation. Indentation not only makes Python code readable, but also distinguishes each block of code from the other. Let's explain this with an example:

def fun():
    pass
for each in "Australia":
    pass

While writing the code, a new block of code starts with a colon followed by a tab. Here, after the function fun(), a colon is provided which will start the function body, pass is part of the function fun() and it is placed at one tab space. Likewise, the for loop starts with a colon. Here, most people get confused whether to use a tab or space. It is advisable to stick to only one type and follow the same across the whole code. If the indentation is not strictly implemented, then code execution will throw an error.