Print with `sep` and `end`

We have seen that when you use the print function to display lists of items you see not only the items converted to strings, but also blanks inserted as item separators, and a newline generated at the end so:

print(1, 2, 3)
print(4, 5, 6)
print(7, 8)

produces

1 2 3
4 5 6
7 8

Though blanks and newlines were inserted automatically, it turns out they are defaults, that the programmer can change.

We have seen optional_parameters. In that section we had default values assigned to the last formal parameters.

The print function also provides defaults for formal parameters: sep=' ' and end=`\n'. Since print takes an arbitrary number of arguments, we cannot just count arguments to the proper position to include new values for sep or end! They are keyword only arguments:: In calling print, you must specifiy the formal parameter name to assign a value as in:

print(1, 2, 3, sep=' and ')
print(4, 5, 6, sep = '')
print(7, 8, sep='***')

which produces

1 and 2 and 3
456
7***8

so the general syntax for using a keyword argument when calling a function is

keywordArgument=value

You must have all three parts. By convention this is the one place you do not put space around the assignment symbol =.

The same ideas apply to the end keyword argument, to replace the standard newline appended at the end of printing:

print(1, 2, 3, end=': also ')
print(4, 5, 6, end='')
print(7, 8, end='and then\n   ')
print(9)

which produces

1 2 3: also 4 5 67 8and then
   9

Look carefully at how the parts run together!

Both keyword arguments can be used together, in either order, but always as the last parameters for print:

print(1, 2, 3, sep=' and ', end=': also ')
print(4, 5, 6, end='', sep='')
print(7, 8, sep='***', end='and then\n   ')
print(9)

which produces

1 and 2 and 3: also 4567***8and then
   9

Note that a newline is explicitly made part of the last end keyword parameter value.

Common examples of use are sep='' when you want no space between items, and end=' ' in a loop where you want one space between items generated in the loop like:

for i in range(5):
    print(i*i, end=' ')
print('is the sequence of squares.')

which produces

0 1 4 9 16 is the sequence of squares.

Print with sep and end

Print with `sep` and `end`