Printing and formatting statements#

Programming for Geoscientists Data Science and Machine Learning for Geoscientists

Basic printing#

Printing text#

A line of code in Python is a statement:

print("Hello world!")

print() is a function in Python that takes an argument in brackets () and prints it out to the terminal.

print("Hello World!")

Hello World!

print() function can also print multiple lines, using \n as a line separator in your text. Notice that you do not need to add spaces around \n in the text:

print("Hello world!\nThis is my first code.\nI love coding.")

Hello world!
This is my first code.
I love coding.

Multiple lines can be also achieved by triple apostrophe """text""":

print("""Hello world! 
This is my first code.
    I love coding.""") # This # is a comment that has no effect on code

# Note how added spaces in the last line are reflected in the printed statement

Hello world! 
This is my first code.
    I love coding.

Printing numbers#

Apart from text, which we call a string, print() function can also take numbers and variables:

print("10")     # Print a string '10'
print(10)       # Print number 10
print(10+5-3)   # Calculate 10+5-3
print(10*5+3/2) # Multiply with *, divide with /
print(10**3)    # To take powers, use **, here 10 to the power of 3

a = 45
print(a)

# Finally more difficult calculation, brackets matter in order of calculation!!

print(5.0*0.6+(100.0+15)/5.0) # With brackets
print(5.0*0.6+100.0+15/5.0)   # Without brackets

String formating#

Sometimes we want to insert certain texts (strings) or numbers into print statements.

Inserting:

use %s in the statement where you want to insert text
use %g in the statement where you want to insert numbers, Python decides here how many significant figures are needed
use %.xf, where x is a number of significant figures you want displayed for your number

The syntax (coding rules) for inserting numbers/text into print statement is:

print("Text %s text text text" % ("text"))

An example below:

# Print your name and age inserted into text

print("My name is %s and I am %g years old." % ("<insert your name>", 18))

# Work out your height in meters, provided you are 5 ft 4 in and insert into text
# 1 foot = 0.3048 m
# 1 inch = 0.0254 m

print("I am %.2f m tall." % (5*0.3048 + 4*0.0254))

My name is <insert your name> and I am 18 years old.
I am 1.63 m tall.

Format() method and f-strings:#

This method allows to specify positions of the objects we want to insert into a string. For example:

print("I like {0} and {1}.".format('dinosaurs', 'brachiopods'))
print("I like {1} and {0}.".format('dinosaurs', 'brachiopods'))

I like dinosaurs and brachiopods.
I like brachiopods and dinosaurs.

We can also specify a variable name that will go into the string:

print("I like {0}, {1} and {other}.".format('dinosaurs', 'brachiopods', other = 'ammonites'))

I like dinosaurs, brachiopods and ammonites.

Recent versions of python also support f-strings which allow us to do the above in a more simple way. They are called f-strings because they require f to be written in front of the quotation marks:

a = 'dinosaurs'
b = 'brachiopods'
c = 'ammonites'

print(f"I like {a}, {b} and {c}.")

I like dinosaurs, brachiopods and ammonites.

Apart from strings, we can also insert numbers:

print(f"This fossil is {0:d} cm long and {1:.2f} cm wide.".format(12, 5.05))
print(f"This fossil is {0:g} cm long and {1:.4f} cm wide.".format(12.0, 5.05))
print(f"This fossil is {0:g} cm long and {1:8.4f} cm wide.".format(12.0, 5.05))

This fossil is 12 cm long and 5.05 cm wide.
This fossil is 12 cm long and 5.0500 cm wide.
This fossil is 12 cm long and   5.0500 cm wide.

All methods are valid so you can use whichever one suits you better!

Exercises#

Print the following:

Veni vidi vici

Anwser

print("Veni vidi vici")

Print the following:
HINT: There are ‘\t’ and ‘\n’ which you might find useful

First line
Second line
	BOOM!

Anwser

print("First line\nSecond line\n\tBOOM!")

Some characters in printing statements can be a bit tricky to handle. Think about the following:

“John is a great fan of Shakespeare, so he decided to reference the famous “Be of not the be?” from ‘The Hamlet’ is his latest essay”

This confuses the Python parser because quotation marks are reserved for the beginning and end of a string. So we use backslash e.g. \" to escape certain characters (like we do with \n and \t). Print the sentence from the example.

Answer

print("John is a great fan of Shakespeare, so he decided to reference the famous \"Be of not the be?\" from \'The Hamlet\' is his latest essay")

Printing can be art! Use some characters to show your creativity! Try a triangle for example:

HINT: What about printing the backslash?

    /\  
   /  \
  /    \  
 /      \  
 --------

Answer

print('''
    /\\
   /  \\
  /    \\
 /      \\
 ---------''')

We had to escape the backslash by putting another backslash in front of it. We could achieve the same with raw strings, which, similarly to f-strings, need to begin with r and they will escape the backslash \ automatically, i.e. the string will be printed raw - exactly as it is written, without any special features like \n and \t.

print(r'''
    /\
   /  \
  /    \
 /      \
 ---------''')

If you want more inspiration, google ASCII art.

        __  _-==-=_,-.
        /--`' \_@-@.--<
        `--'\ \   <___/.  
             \ \\   " /  
              >=\\_/`<
  ____       /= |  \_|/
_'    `\   _/=== \___/
`___/ //\./=/~\====\
    \   // /   | ===:
     |  ._/_,__|_ ==:        __
      \/    \\ \\`--|       / \\
       |    _     \\:      /==:-\
       `.__' `-____/       |--|==:
          \    \ ===\      :==:`-'
          _>    \ ===\    /==/
         /==\   |  ===\__/--/
        <=== \  /  ====\ \\/
        _`--  \/  === \/--'
       |       \ ==== |
        -`------/`--' /
                \___-'

ESE Jupyter Material

Printing and formatting statements

Contents

Printing and formatting statements#

Basic printing#

Printing text#

Printing numbers#

String formating#

Format() method and f-strings:#

Exercises#