Python str.format string start at a fixed spacing

Question

I want to output the following format:

addr<-9->bit<-15->value<-13->name<-26->type
....     ...      ......     ......    ......   #..... is the content of each row

I used the str.format to achieve it:

STRING_FORMATTER = '{0:13}{1:18}{2:18}{3:30}{4:10}\n'
content = STRING_FORMATTER.format('addr', 'bit', 'value', 'name', 'type')
content = content + STRING_FORMATTER.format('0123', 'LONG STRING THAT EXCEEDS 18 SPACES!!!!!!!!!!!!!!!!', '', '', 'reg')
content = content + STRING_FORMATTER.format('00', '0', '0xAD', 'NAME', 'bit')
.....

I basically construct the string by the type. The above is a problem that when the 2nd string exceeds 18 char spaces, the string behind is pushed. Is there a way to solve it?

Or is there a better way to format the string to start at a fixed spacing in front?

I do not want that to be cut off, I want the Long string to start at 14, and it has a size 18+18+30. And I want the type exactly align with the first line — Allen W
– Allen W, Commented Dec 15, 2017 at 1:33

Mark Tolonen · Accepted Answer · 2017-12-15 01:59:42Z

To do what you want requires splitting the string across the three fields. The syntax used below requires Python 3.5 or later for the PEP 448 - Additional Unpacking Generalizations feature used. The function breaks a string into the correct field widths for the three fields being spanned:

STRING_FORMATTER = '{0:13}{1:18}{2:18}{3:30}{4:10}\n'

def split(s,*widths):
    current = 0
    for width in widths:
        yield s[current:current + width]
        current += width

content = STRING_FORMATTER.format('addr', 'bit', 'value', 'name', 'type')
content += STRING_FORMATTER.format('0123', *split('LONG STRING THAT EXCEEDS 18 SPACES!!!!!!!!!!!!!!!!',18,18,30), 'reg')
content += STRING_FORMATTER.format('00', '0', '0xAD', 'NAME', 'bit')
print(content)

Output:

addr         bit               value             name                          type
0123         LONG STRING THAT EXCEEDS 18 SPACES!!!!!!!!!!!!!!!!                reg
00           0                 0xAD              NAME                          bit

James · Accepted Answer · 2017-12-15 01:34:37Z

2

You can construct a function to truncate strings that are too long, and wrap that around the format inputs.

def truncate(*inputs, max_length=18):
    return tuple(s[:max_length] for s in inputs)

STRING_FORMATTER = '{0:13}{1:18}{2:18}{3:30}{4:10}\n'
content = STRING_FORMATTER.format(
    *truncate('addr', 'bit', 'value', 'name', 'type'))
content = content + STRING_FORMATTER.format(
    *truncate('0123', 'LONG STRING THAT EXCEEDS 18 SPACES!!!!!!!!!!!!!!!!', '', '', 'reg'))
content = content + STRING_FORMATTER.format(
    *truncate('00', '0', '0xAD', 'NAME', 'bit'))

answered Dec 15, 2017 at 1:34

James

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