Difference between revisions of "Python-3.4.3/C3/Input-output/English"

Learning Objectives

• Print some values
• Print using format specifiers
• Take input from user and
• Display a prompt to the user before taking the input

System Specifications

• Ubuntu Linux 16.04 operating system
• Python 3.4.3 and
• IPython 5.1.0

Pre-requisite slide

• You should know how to run basic Python commands on the ipython console.

If not, see the relevant Python tutorials on this website.

ipython3

Open the terminal.

Type ipython3 and press Enter.

From here onwards, remember to press the Enter key after typing every command on the terminal.

Type, a is equal to inside double quotes This is a string

Highlight the output

Highlight the output of a

Highlight the output of print(a)

This also prints the value of a.

But there is a difference in the outputs.

Typing just a displays the content of a.

The statement print inside parentheses a prints the string itself.

We can see the difference clearly when we use strings with new lines in them.

Highlight the output

As you can see, it just shows that b contains a newline character.

Highlight the output.

It prints the string, A line and then New line in the next line.

print statement in Python supports string formatting.

<<PAUSE>>

Formatting operations

Percentage string operator is called as format operator.

For example:

• Percentage d - specifies the integer format
• Percentage s - specifies the string format and
• Percentage f - denotes the float format

print('The value of x is %3.2f' %x)

Highlight %3.2f

To print the value of x, type as shown.

Here percentage 3.2f specifies the output in float and .2f rounds off the value to two decimal point.

Highlight .4f

Type as shown.

Here, it rounds off to four decimal places.

Type, y is equal to 2

Type, print (''x is %2.1f, y is %d, z is %s''%(x,y,z))

Highlight%2.1f, %d, %s

Various arguments can be passed to print using modifiers.

The values of x, y and z are substituted in place of the format specifiers as

• percentage 2.1f,
• percentage d and
• percentage s

respectively.

<<PAUSE>>

Exercise 1

Try this exercise and then resume the video.

What happens when you execute the following?

Highlight %d, %f

Highlight 2.000000

Here the int value of x and float value of y are printed as per the format specifiers.

It prints six decimal places by default for float.

print ("Hello")

print ("World")

print ("Hello",end=' ')

print ("World")

Now we will see how to suppress the newline character.

Open a text editor and type the following code.

Highlight space in between Hello and world

We can see that the print statement prints a space instead of a new line.

<<PAUSE>>

We will use the input function for this.

Type ip is equal to input open and close parentheses

Type an input

Type, an input and press Enter.

Highlight the outpt

Type ip

We can see that it contains the string - an input

Exercise 2

Try this exercise and then resume the video.

Enter the number 5.6 as input and store it in a variable c.

Type, c is equal to input open and close parentheses

Highlight the output

Type, type inside parentheses c

We see that c is a string.

Because input command always takes the input as string no matter whatever is the input.

Exercise 3

Try this exercise and then resume the video.

Execute the below statement.

What happens when you do not enter anything and hit Enter?

<press enter>

Press Enter without giving any input.

Again press Enter to get the prompt.

Highlight the output

When nothing is entered, an empty string is considered as input.

<<PAUSE>>

Now we will give a prompt to get the input.

Type ip is equal to input inside parentheses inside double quotes Please enter a number forward slash n

This is how we can display a prompt to get input from user.

Summary slide

In this tutorial, we have learnt to,

• Use print statement
• Use the format specifiers percentage d, percentage f and percentage s in the print statement
• Take input from user by using input function and
• Display a prompt to the user before taking the input

Evaluation

1. a is equal to input open and close parentheses and user enters 2.5. What is the type of a?
2. If a is equal to 2 and b is equal to 4.5, what is the result of the following action?

Solutions

1. No matter what you enter, it will be taken as a string. Hence 2.5 is a string.
2. Since b is called first, it will display integer value of b. Because the modifier used is percentage d.

Similarly, float value of a will be displayed due to its modifier percentage 2.1f. Hence the output is a is 4 and b is 2.0

Acknowledgement

For more details, visit this website.

Thank You

Thanks for watching.