knowledge-kitchen / course-notes

Strings - Formatting

Examples of formatting strings in Python using the built-in string format() function.

• The expected output of each example is displayed as a comment.
• Note that the format function always returns a string.

The basic idea

Unlabeled placeholders:

x = '{}, {}, {}'.format('a', 'b', 'c')
print(x)
#'a, b, c'

Numerical indices as placeholders

x = '{0}, {1}, {2}'.format('a', 'b', 'c')
print(x)
#'a, b, c'

Named placeholders:

x = '{first}, {second}, {third}'.format(first='a', second='b', third='c')
print(x)
#'a, b, c'

Mixing it up

Numerical indices out of order:

x = '{2}, {1}, {0}'.format('a', 'b', 'c')
print(x)
#'c, b, a'

Repeating placeholders more than once:

x = '{0}{1}{0}'.format('abra', 'cad')
print(x)
#'abracadabra'

Alignment

Left-aligned within 20 spaces:

x = format('Harry', '<20s')
print(x)
#'Harry '

Right-aligned within 20 spaces:

x = format('Barry', '>20s')
print(x)
#' Barry'

Center-aligned within 20 spaces:

x = format('Harry', '^20s')
print(x)
#' Harry '

Right-aligned within 20 spaces with the '*' as a fill character:

x = format('Harry', '*>20s')
print(x)
#'***************Harry'

Center-aligned within 20 spaces with the '-' as a fill character:

x = format('Barry', '-^20s')
print(x)
#'-------Barry--------'

Combining formatted strings

A string left-aligned within 20 spaces, combined with another string left-aligned within 10 spaces:

x = format('Harry', '<20s')
y = format('$20', '<10s')
z = "{0}{1}".format(x, y) #`[` remember`` ``this `](#The_basic_idea)`?!
print(z)
#'Harry $20 '

Limiting decimal places

Two decimal places:

x = format(0.33333333, '.2f')
print(x)
#'0.33'

Five decimal places:

x = format(0.33333333, '.5f')
print(x)
#'0.33333'

Commas for thousands:

x = format(33333333.22222222, ',.5f')
print(x)
#'33,333,333.22222'

Right-aligned:

x = format (33333333.22222222, '>20,.2f')
print(x)
# ' 33,333,333.22'

Percentage conversion:

x = format(0.52, '%')
print(x)
#'52.000000%'

Percentage conversion with limited decimal places:

x = format(0.52, '.2%')
print(x)
#'52.00%'

Percentage conversion with no decimal places:

x = format(0.52, '.0%')
print(x)
#'52%'

Left-aligned with percentage conversion and limited decimal places:

x = format(0.52, '<20.2%')
print(x)
#'52.00% '

Integer numbers with commas

An integer, with commas for thousands:

x = format(5200, ',d')
print(x)
#'5,200'

An integer, with commas for thousands, left-aligned within 20 spaces:

x = format(5200, '<20,d')
print(x)
#'5,200 '

An integer, with commas for thousands, right-aligned within 20 spaces:

x = format(5200, '>20,d')
print(x)
#' 5,200'