"""General floating point formatting functions.

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Functions:

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fix(x, digits_behind)

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sci(x, digits_behind)

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Each takes a number or a string and a number of digits as arguments.

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Parameters:

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x: number to be formatted; or a string resembling a number

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digits_behind: number of digits behind the decimal point

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"""

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from warnings import warnpy3k

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warnpy3k("the fpformat module has been removed in Python 3.0", stacklevel=2)

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del warnpy3k

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import re

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__all__ = ["fix","sci","NotANumber"]

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# Compiled regular expression to "decode" a number

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decoder = re.compile(r'^([-+]?)0*(\d*)((?:\.\d*)?)(([eE][-+]?\d+)?)$')

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# \0 the whole thing

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# \1 leading sign or empty

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# \2 digits left of decimal point

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# \3 fraction (empty or begins with point)

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# \4 exponent part (empty or begins with 'e' or 'E')

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try:

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class NotANumber(ValueError):

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pass

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except TypeError:

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NotANumber = 'fpformat.NotANumber'

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def extract(s):

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"""Return (sign, intpart, fraction, expo) or raise an exception:

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sign is '+' or '-'

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intpart is 0 or more digits beginning with a nonzero

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fraction is 0 or more digits

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expo is an integer"""

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res = decoder.match(s)

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if res is None: raise NotANumber, s

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sign, intpart, fraction, exppart = res.group(1,2,3,4)

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if sign == '+': sign = ''

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if fraction: fraction = fraction[1:]

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if exppart: expo = int(exppart[1:])

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else: expo = 0

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return sign, intpart, fraction, expo

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def unexpo(intpart, fraction, expo):

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"""Remove the exponent by changing intpart and fraction."""

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if expo > 0: # Move the point left

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f = len(fraction)

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intpart, fraction = intpart + fraction[:expo], fraction[expo:]

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if expo > f:

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intpart = intpart + '0'*(expo-f)

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elif expo < 0: # Move the point right

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i = len(intpart)

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intpart, fraction = intpart[:expo], intpart[expo:] + fraction

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if expo < -i:

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fraction = '0'*(-expo-i) + fraction

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return intpart, fraction

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def roundfrac(intpart, fraction, digs):

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"""Round or extend the fraction to size digs."""

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f = len(fraction)

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if f <= digs:

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return intpart, fraction + '0'*(digs-f)

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i = len(intpart)

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if i+digs < 0:

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return '0'*-digs, ''

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total = intpart + fraction

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nextdigit = total[i+digs]

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if nextdigit >= '5': # Hard case: increment last digit, may have carry!

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n = i + digs - 1

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while n >= 0:

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if total[n] != '9': break

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n = n-1

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else:

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total = '0' + total

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i = i+1

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n = 0

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total = total[:n] + chr(ord(total[n]) + 1) + '0'*(len(total)-n-1)

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intpart, fraction = total[:i], total[i:]

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if digs >= 0:

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return intpart, fraction[:digs]

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else:

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return intpart[:digs] + '0'*-digs, ''

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def fix(x, digs):

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"""Format x as [-]ddd.ddd with 'digs' digits after the point

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and at least one digit before.

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If digs <= 0, the point is suppressed."""

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if type(x) != type(''): x = repr(x)

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try:

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sign, intpart, fraction, expo = extract(x)

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except NotANumber:

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return x

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intpart, fraction = unexpo(intpart, fraction, expo)

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intpart, fraction = roundfrac(intpart, fraction, digs)

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while intpart and intpart[0] == '0': intpart = intpart[1:]

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if intpart == '': intpart = '0'

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if digs > 0: return sign + intpart + '.' + fraction

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else: return sign + intpart

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def sci(x, digs):

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"""Format x as [-]d.dddE[+-]ddd with 'digs' digits after the point

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and exactly one digit before.

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If digs is <= 0, one digit is kept and the point is suppressed."""

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if type(x) != type(''): x = repr(x)

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sign, intpart, fraction, expo = extract(x)

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if not intpart:

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while fraction and fraction[0] == '0':

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fraction = fraction[1:]

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expo = expo - 1

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if fraction:

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intpart, fraction = fraction[0], fraction[1:]

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expo = expo - 1

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else:

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intpart = '0'

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else:

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expo = expo + len(intpart) - 1

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intpart, fraction = intpart[0], intpart[1:] + fraction

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digs = max(0, digs)

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intpart, fraction = roundfrac(intpart, fraction, digs)

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if len(intpart) > 1:

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intpart, fraction, expo = \

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intpart[0], intpart[1:] + fraction[:-1], \

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expo + len(intpart) - 1

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s = sign + intpart

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if digs > 0: s = s + '.' + fraction

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e = repr(abs(expo))

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e = '0'*(3-len(e)) + e

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if expo < 0: e = '-' + e

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else: e = '+' + e

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return s + 'e' + e

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def test():

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"""Interactive test run."""

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try:

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while 1:

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x, digs = input('Enter (x, digs): ')

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print x, fix(x, digs), sci(x, digs)

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except (EOFError, KeyboardInterrupt):

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pass

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