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Python: input () and print () function

 

Python Basic Tutorial

 
 
 
 
 

The input () function:

  • The purpose of input() function is to read input from the standard input (the keyboard, by default).

    It accepts all user input as a string.

  • The user may enter a number or a string but the input() function treats them as strings only.

The general format is:

input([prompt])

Here,
The prompt is an optional parameter and where prompt is the string you wish to display on the screen.

For example,

Inputting Numeric Values

Suppose we want to find the sum of two numbers and the program is:

When we execute the above program, the program doesn’t add the two numbers together; it just puts one right after the other as 1020

The solution to the above problem is:

Python offers two functions int() and float() to be used with input ( ) to convert the values received through input ( ) into int and float types.

Accept an Integer input from User

We need to convert an input string value into an integer using an int() function.

# Both input values are converted into integer type

num1 = int (input("Enter first number: "))

num2 = int(input("Enter second number: "))

sum = num1 + num2

print ('The sum of ', num1, ' and ', num2, ' is ',sum)

OUTPUT:

Enter the first number: 10

Enter second number: 30

The sum of 10 and 30 is 40

Accept a float input from User

We need to convert an input string value into a float using a float() function.

# Both input values are converted into float type

num1 = float (input("Enter first number: "))

num2 = float(input("Enter second number: "))

sum = num1 + num2

print ('The sum of ', num1, ' and ', num2, ' is ',sum)

OUTPUT:

Enter the first number: 10.5

Enter second number: 30.5

The sum of 10 and 30 is 41.0

Get multiple input values from a user in one line

In Python, we can accept two or three values from the user in one input() call.

name,Class,Marks = input("Enter your Name,Class,Marks separated by space: ").split()

print("User Details: ",name, Class,Marks)

OUTPUT:

Enter your Name,Class,Marks separated by space: Ashaz 4 98

User Details: Ashaz 4 98

The print () function

  • The print ( ) function allows you to print out the value of a variable and strings in parenthesis.

  • The print() function will print as strings everything in a comma-separated sequence of expressions, and it will separate the results with single blanks by default.

  • The print() function prints strings in between quotes (either single or double). If a print statement has quotes around text, the computer will print it out just as it is written.

  • To print multiple items, separate them with commas. The print() function inserts a blank between objects.

  • The print() function automatically appends a newline to output. To print without a newline, use end separator after the last object.

The general form of print () function is:

print ( )

print (value/expr)

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

Where,

sep: The optional parameter sep is a separator between the output values. We can use a character, integer or a string as a separator. The default separator is space.
end: This is also optional and it allows us to specify any string to be appended after the last value. The default is a new line.

• The file is the object where the values are printed and its default value is sys.stdout (screen).

• flush force it to "flush" the buffer, meaning that it will write
everything in the buffer to the terminal, even if normally waits before doing so.

Uses and Examples of print() function in Python

1) The print ( ) function can be used to print a blank line.

For example:

print('Learn python from')

print() # it print a blank line in between two print statement

print('https://www.learnpython4cbse.com')

OUTPUT:

Learn python from

https://www.learnpython4cbse.com

2) The print() function prints the value of variable.

For example:

N1 = 20

N2 = 30
Sum = N1 + N2

print(Sum) # prints a value​

The above print statement receives a variable Sum 

3) The print() function prints the value of an expression.

For example:

N1 = 20

N2 = 30

print(N1 + N2) # prints a value of an expression i.e., N1+N2

The above print statement prints a value of an expression

OUTPUT:

50

4) The print() function prints two values separated with comma (,)

For example:

Ver = 3.9
lang =
'Python'
print (lang, Ver) # prints two values separated with comma (,)

OUTPUT:

Python 3.9

5) The print() function prints a message 

For example:

N1 =20

N2 = 30

sum = N1 + N2

print ('The sum of two numbers is')

# print statement receives a string message

print (sum)

OUTPUT:

The sum of two numbers is

50

6) The print() function prints a value, message or both message and values and vice versa.

For example:

N1 = 20

N2 = 30

Sum = N1 + N2

print ('The sum of two numbers is', Sum)

# print is alternate way

print(Sum, "is the sum of", N1, "and", N2)

print() with Concatenate Operator (+)

  • The print() function can print two strings either using comma (,) operator, or a concatenate operator (+).

  • When we use a concatenate operator (+) between two strings, both the strings are joined without leaving any space.

  • Do not use the concatenate operator (+) with the combination of numeric and string data.

  • If you do so then the Python interpreter will produce an error as Can't convert 'int' object to str implicitly, i.e., cannot concatenate 'str' and 'int' objects.

 

For example:

print("I Learn Python", "with learnpython4cbse.com")

# Print with a space separator.
will produce:

I Learn Python with learnpython4cbse.com

Similarly, by using the concatenate operator (+), the print() function is:
print("I Learn Python" + "with learnpython4cbse.com")

# Print without a separator.
will produce:
I Learn Pythonwith learnpython4cbse.com

Print with Keyword Parameter sep and end

The print() function has two keyword arguments sep and end to handle the complex jobs for us to print standard output. Keyword parameters must be listed at the end of the parameter list. These are:

sep: 

  • Defines the string that is to be placed between every two values printed.

  • By default, sep inserts a space (‘ ’).

  • If the sep option is missing, space is printed between the values received by print() function.

For example:

# It specifies the separator between the outputted arguments.

print('H','e','l','l','o',sep='-')
will produce:
H-e-l-l-o

print("My", "name", "is", "Stephen", sep="*")

will produce:

My*name*is*Stephen

end: 

  • This separator defines the string to be printed at the end of the print() function.

  • By default, end inserts a new line ('\n').

  • If you don't supply the end option, a newline is printed by default.

  • The string assigned to the end keyword argument can be of any length

For example:

print("My name is Stephen", end = ' ')

print("and learn python")

will produce:

My name is Stephen and learn python

If we wish to print the first two lines in one line and last two lines in another line with a comma (,) and space separator, then the code will be written as:

print("My name is A. Khan", end = ', ')

print("Class-XII A.")

print("I am in Sr. Sec. School", end = ', ')

print("Delhi, India.")

will produce:

My name is A. Khan, Class-XII A.
I am in Sr. Sec. School, Delhi, India.

 
 
 
 

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