python - How to pad leading zero (in a function) dynamically? -

i know "%03d" can pretty easily, i'm trying solve different problem. part of script, need find out how many numbers in range (e.g. 0-999) have @ lest 1 3 (or digit in question) in it. so, came lambda function:

fx = lambda z,y=999: [ "%03d" % (x, ) x in range(y) if str(z) in str(x) ] 

which working great want automate padding 'leading zero' bit according range e.g. 003 when it's 999 or 09 88 , on. idea how can that?

if want pass dynamic width formatting functions, can:

>>> width = 5 >>> value = 2 >>> '%0*d' % (width, value) '00002' 

it's easier new-style formatting, because can embed placeholders inside placeholders:

>>> width = 5 >>> value = 2 >>> '{1:0{0}}'.format(width, value) '00002' 

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if want know how longest value in of values before outputting them, long can iterate on values twice, that's pretty easy:

>>> values = 3, 100, 50000 >>> width = max(len('%0d' % value) value in values) >>> ', '.join('%0*d' % (width, value) value in values) '00003, 00100, 50000' 

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and if want base on parameter, that's easier:

fx = lambda z,y=999: [ "%0*d" % (len('%0d' % y), x) x in range(y) if str(z) in str(x) ] 

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however, that's going calculate width of y on , on again, because inside expression there's no easy way store it, , lambda can take expression.

which raises question of why you're using lambda in first place. advantage of lambda on def can use in expression , don't need come name it. if you're going assign name, eliminates both advantages. so, this:

def fx(z, y=999):     width = len('%0d' % y)     return ["0%*d" % (width, x) x in range(y) if str(z) in str(x)]