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Python Intro



All the IPython Notebooks in this lecture series are available at https://github.com/rajathkumarmp/Python-Lectures

#Print Statement

The print statement can be used in the following different ways :

- print "Hello World"
- print "Hello", <Variable Containing the String>
- print "Hello" + <Variable Containing the String>
- print "Hello %s" % <variable containing the string>
print "Hello World"
Hello World

In Python, single, double and triple quotes are used to denote a string. Most use single quotes when declaring a single character. Double quotes when declaring a line and triple quotes when declaring a paragraph/multiple lines.

print 'Hey'
Hey
print """My name is Rajath Kumar M.P.

I love Python."""
My name is Rajath Kumar M.P.

I love Python.

Strings can be assigned to variable say string1 and string2 which can called when using the print statement.

string1 = 'World'
print 'Hello', string1

string2 = '!'
print 'Hello', string1, string2
Hello World
Hello World !

String concatenation is the “addition” of two strings. Observe that while concatenating there will be no space between the strings.

print 'Hello' + string1 + string2
HelloWorld!

%s is used to refer to a variable which contains a string.

print "Hello %s" % string1
Hello World

Similarly, when using other data types

- %s -> string
- %d -> Integer
- %f -> Float
- %o -> Octal
- %x -> Hexadecimal
- %e -> exponential

This can be used for conversions inside the print statement itself.

print "Actual Number = %d" %18
print "Float of the number = %f" %18
print "Octal equivalent of the number = %o" %18
print "Hexadecimal equivalent of the number = %x" %18
print "Exponential equivalent of the number = %e" %18
Actual Number = 18
Float of the number = 18.000000
Octal equivalent of the number = 22
Hexadecimal equivalent of the number = 12
Exponential equivalent of the number = 1.800000e+01

When referring to multiple variables parenthesis is used.

print "Hello %s %s" %(string1,string2)
Hello World !

##Other Examples

The following are other different ways the print statement can be put to use.

print "I want %%d to be printed %s" %'here'
I want %d to be printed here
print '_A'*10
_A_A_A_A_A_A_A_A_A_A
print "Jan\nFeb\nMar\nApr\nMay\nJun\nJul\nAug"
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
print "I want \\n to be printed."
I want \n to be printed.
print """
Routine:
\t- Eat
\t- Sleep\n\t- Repeat
"""
Routine:
	- Eat
	- Sleep
	- Repeat

#PrecisionWidth and FieldWidth

Fieldwidth is the width of the entire number and precision is the width towards the right. One can alter these widths based on the requirements.

The default Precision Width is set to 6.

"%f" % 3.121312312312
'3.121312'

Notice upto 6 decimal points are returned. To specify the number of decimal points, ‘%(fieldwidth).(precisionwidth)f’ is used.

"%.5f" % 3.121312312312
'3.12131'

If the field width is set more than the necessary than the data right aligns itself to adjust to the specified values.

"%9.5f" % 3.121312312312
'  3.12131'

Zero padding is done by adding a 0 at the start of fieldwidth.

"%020.5f" % 3.121312312312
'00000000000003.12131'

For proper alignment, a space can be left blank in the field width so that when a negative number is used, proper alignment is maintained.

print "% 9f" % 3.121312312312
print "% 9f" % -3.121312312312
 3.121312
-3.121312

’+’ sign can be returned at the beginning of a positive number by adding a + sign at the beginning of the field width.

print "%+9f" % 3.121312312312
print "% 9f" % -3.121312312312
+3.121312
-3.121312

As mentioned above, the data right aligns itself when the field width mentioned is larger than the actualy field width. But left alignment can be done by specifying a negative symbol in the field width.

"%-9.3f" % 3.121312312312
'3.121    '