Python Input, Output, and Import

Python Input, Output, and Import: This tutorial focuses on two built-in functions print() and input() to perform the I/O task in Python. Also, you will learn to import modules and use them in your program.

Python provides various built-in functions that are promptly accessible to us at the Python prompt.

Some of the function like input() and print() is generally used for standard info and yield tasks individually. Let us see the output segment first.

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Python Output Using print() function

We use the print() function to output data to the standard output device (screen). We can also output data to a file, however, this will be discussed later.

An example of its use is given below.

print('This sentence is output to the screen')

Output

This sentence is output to the screen

Another example is given below:

a = 5
print('The value of a is', a)

Output

The value of a is 5

In the second print() statement, we can see that space was included between the string and the value of variable a. This is by default but we can’t change it.

The actual syntax of the print() function is:

print(*objects, sep=' ', end='\n', file=sys.stdout, flush=False)

Here, objects are the value(s) to be printed.

The sep separator is used between the qualities. It defaults into a space character.

After all, values are printed, the end is printed. It defaults into another line.

The file is the object where the values are printed and its default esteem is sys.stdout (screen). Here is an example to illustrate this.

print(1, 2, 3, 4)
print(1, 2, 3, 4, sep='*')
print(1, 2, 3, 4, sep='#', end='&')

Output

1 2 3 4
1*2*3*4
1#2#3#4&

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Output formatting

Sometimes we would like to format our output to make it look attractive. This can be done by using the str.format() method. This method is visible to any string object.

>>> x = 5; y = 10
>>> print('The value of x is {} and y is {}'.format(x,y))
The value of x is 5 and y is 10

Here, the curly braces {} are used as placeholders. We can specify the order in which they are printed by using numbers (tuple index).

print('I love {0} and {1}'.format('bread','butter'))
print('I love {1} and {0}'.format('bread','butter'))

Output

I love bread and butter
I love butter and bread

We can even use keyword arguments to format the string.

>>> print('Hello {name}, {greeting}'.format(greeting = 'Goodmorning', name = 'salman'))
Hello salman, Goodmorning

We can also format strings like the old sprintf() style used in the C programming language. We use the % operator to accomplish this.

>>> x = 12.3456789
>>> print('The value of x is %3.2f' %x)
The value of x is 12.35
>>> print('The value of x is %3.4f' %x)
The value of x is 12.3457

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Python Input

Up until now, our programs want static. The estimation of factors was characterized or hardcoded into the source code.

To allow flexibility, we should take the input from the client. In Python, we have the input() function to allow this. The syntax for input() is:

input([prompt])

where prompt is the string we wish to display on the screen. It is optional.

>>> num = input('Enter a number: ')
Enter a number: 10
>>> num
'10'

Here, we can see that the entered value 10 is a string, not a number. To convert this into a number we can use int() or float() functions.

>>> int('10')
10
>>> float('10')
10.0

This same operation can be performed using the eval() function. But eval takes it further. It can evaluate even expressions, provided the input is a string

>>> int('2+3')
Traceback (most recent call last):
  File "<string>", line 301, in runcode
  File "<interactive input>", line 1, in <module>
ValueError: invalid literal for int() with base 10: '2+3'
>>> eval('2+3')
5

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Python Import

When our program develops greater, it is a smart thought to break it into various modules.

A module is a file containing Python definitions and statements. Python modules have a filename and end with the expansion .py.

Definitions inside a module can be imported to another module or the intelligent mediator in Python. We use the import watchword to do this.
For instance, we can import the math module by composing the following line:

import math

We can use the module in the following ways:

import math
print(math.pi)

Output

3.141592653589793

Presently all the definitions inside the math module are accessible in our degree. We can also import some particular attributes and function only, using the from the keyboard. For instance:

>>> from math import pi
>>> pi
3.141592653589793

While importing a module, Python looks at several places defined in sys.path. It is a list of directory locations.

>>> import sys
>>> sys.path
['', 
 'C:\\Python33\\Lib\\idlelib', 
 'C:\\Windows\\system32\\python33.zip', 
 'C:\\Python33\\DLLs', 
 'C:\\Python33\\lib', 
 'C:\\Python33', 
 'C:\\Python33\\lib\\site-packages']

We can also add our own location to this list.

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Please feel free to give your comment if you face any difficulty here.

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