3.1.2. Comments, Strings and Print Statements¶

3.1.2.1. Comments¶

Non-computational parts of the program that textually describe the behaviour of the program.
Comments begin with # everything to right of the hash is ignored by Python.
Comments should be frequent so you and others can understand the code.

# Did you notice that these words are green? Any words after
# a Hash Tag (#) on the same line are called comments.

# Comments are lines of code that the computer does not
# look at. These can be used to clarify the purpose of your
# code and make it easier to read.

3.1.2.2. Strings¶

Sequence of characters enclosed by a pair of single or double quotes
Examples are “cats hate dogs” and ‘Strings are fun!’.
Strings are one kind of data in Python. Their data type is denoted str.

print "This is a string"

This is a string

print 'This is also a string'

This is also a string

3.1.2.3. Print Statements¶

To print these strings and other things to the box on the right, the word print is used.

print "Output Number One"
print 5.069393

Output Number One
5.069393

3.1.2.3.1. Blank Lines¶

Print statements on their own can be used to print blank lines to the screen, which separates output and makes it easier to read.

print
print "Hello"
print

<BLANKLINE>
Hello
<BLANKLINE>

3.1.2.3.2. Strings on the Same Line¶

Multiple strings can be printed on the same line by using commas to separate them. This automatically inserts a space in between the two strings.

print "One", "Two"
print "One","Two","Three"

One Two
One Two Three

3.1.2.3.3. Strings within Strings¶

If you want to include a quotation mark or apostrophe in your string, you need to make the symbols around the string be the opposite type.

print "'You're awesome!' he said"
print '"Thank you!" I replied.'

'You're awesome!' he said
"Thank you!" I replied.

3.1.2.3.4. Errors with String Value¶

If you accidentally use the same ones, errors can occur.
Notice that the words are not coloured in the following examples; that is a big clue that something is wrong.

print 'It's mine'
print "I said "hi" to him"

  File "<ipython-input-15-a5c49eea454d>", line 1
    print 'It's mine'
              ^
SyntaxError: invalid syntax

3.1.2.3.5. Errors with Print Command¶

You can also get an error by misspelling ‘print.’ Notice that again, print shows up as a different colour than normal.

prit "Error"
printer "Error"

  File "<ipython-input-16-abc799b605cb>", line 1
    prit "Error"
               ^
SyntaxError: invalid syntax

3.1.2.3.6. Concatenate Multiple Lines on Print Command¶

You can concatenate the output of a print command over multiple lines of code using the comma , and on the same line using the plus sign +

print "Something is " + str(42) + " and",    # Notice that the comma is used
print "Something else is " + str(60)

Something is 42 and Something else is 60

Note: str does not add a space before and after the string
Commas within and between print statements do add a space

print "something",
print "something else"
print "--"
print "this","and","that"

something something else
--
this and that