# Comments are preceded by the hashtag (pound sign)
# Comments extend from the hashtag off to the end of the line

numeralCharacters = '0123456789' # assign a string of characters to numeralCharacters
print 'numeralCharacters: ' + numeralCharacters # print the value of the string variable numeralCharacters

# Assign the first 3 characters of numeralCharacters to first3Chars
# Note that the numbers in square brackets are 0-base indexes.
# Position 0 in the string is occupied by the first character.
# Think of an index as being the distance, in characters, from the beginning
#  of the string. This will also be useful for other kinds of data later on.
# In numeralCharacters, the first character in the string is '0' and the last
# character is '9'. To extract a range of characters from a string and
# optionally assign them to another, use a 'slicing' operation like this:

first3Chars = numeralCharacters[0:3]

# where [0:3] following the string variable says 'starting at position 0,
# extract the characters up to but not including the character in position 3.
# Now we can print the result to see how python interpreted our code:

print 'first 3 characters: ' + first3Chars

# Now lets pull out characters from the middle of numeralCharacters:

middleChars = numeralCharacters[4:7]

# This can get confusing so let's thing about this very carefully by mapping
# out each character in numeralCharacters to a position:

# Position: 0   1   2   3   4   5   6   7   8   9
# Value:    0   1   2   3   4   5   6   7   8   9

# Therefore, numeralCharacters[4:7] extracts the following range:

# Position: 0   1   2   3   4   5   6   7   8   9
# Value:    -   -   -   -   4   5   6   -   -   -

# Why does the range go up to 7 but not include it? I ask myself the same
# question all the time. That's just how the operation is defined.
# Fortunately, similar operations in other programming languages
# behave the same way. Let's print the results, though, just to make sure:

print 'middleChars: ' + middleChars