我需要找到一种方法在python中转换以下字符串：
0.000 => 0
0 => 0
123.45000 => 123.45
0000 => 0
123.4506780 => 123.450678
等等。我试过 .rstrip('0').rstrip('.')，但如果输入为 0 或 00 则不起作用。
有什么想法吗？谢谢！
【问题讨论】：
更新泛化以保持精度和处理看不见的值：
import decimal
import random
def format_number(num):
try:
dec = decimal.Decimal(num)
except:
return 'bad'
tup = dec.as_tuple()
delta = len(tup.digits) + tup.exponent
digits = ''.join(str(d) for d in tup.digits)
if delta <= 0:
zeros = abs(tup.exponent) - len(tup.digits)
val = '0.' + ('0'*zeros) + digits
else:
val = digits[:delta] + ('0'*tup.exponent) + '.' + digits[delta:]
val = val.rstrip('0')
if val[-1] == '.':
val = val[:-1]
if tup.sign:
return '-' + val
return val
# test data
NUMS = '''
0.0000 0
0 0
123.45000 123.45
0000 0
123.4506780 123.450678
0.1 0.1
0.001 0.001
0.005000 0.005
.1234 0.1234
1.23e1 12.3
-123.456 -123.456
4.98e10 49800000000
4.9815135 4.9815135
4e30 4000000000000000000000000000000
-0.0000000000004 -0.0000000000004
-.4e-12 -0.0000000000004
-0.11112 -0.11112
1.3.4.5 bad
-1.2.3 bad
'''
for num, exp in [s.split() for s in NUMS.split('\n') if s]:
res = format_number(num)
print res
assert exp == res
输出：
0
0
123.45
0
123.450678
0.1
0.001
0.005
0.1234
12.3
-123.456
49800000000
4.9815135
4000000000000000000000000000000
-0.0000000000004
-0.0000000000004
-0.11112
bad
bad
【讨论】：
str(float('.1234567890123456')) 产生 '0.123456789012' 失败
0.00000000023283064365386963 产生 2.3283064365386963E-1 构成双桶 FAIL
format_number() 为某些数字（如 12.5E154 或 0.0068E-47）返回的表示是不切实际的。相反，需要有一个相反的功能：以短符号压缩长数字字符串，就像 arrussel84 的 '{:g}'.format() 所做的那样。顺便说一句，它只处理数字字符串；它无法在文本中搜索它们。
您可以根据需要使用format strings，但请注意，您可能需要设置所需的精度，因为默认情况下格式字符串有自己的逻辑。 Janneb 建议 another answer 的精度为 17。
'{:g}'.format(float(your_string_goes_here))
不过，在考虑了更多之后，我认为最简单和最好的解决方案就是将字符串转换两次（如jathanism suggests）：
str(float(your_string_goes_here))
编辑：由于评论而添加了说明。
【讨论】：
对于浮点数，您只需将字符串转换为float：
>>> float('123.4506780')
123.450678
对于零值，您可以将它们转换为整数：
>>> int('0000')
0
打印时，数值会自动转换为字符串。如果您需要这些实际上是字符串，您可以简单地将它们转换回带有str() 的字符串，例如：
>>> str(float('123.4506780'))
'123.450678'
【讨论】：
'%.17g' % float(mystr)
取决于你真正想要做什么..
【讨论】：
'%g' % 1.23456789, str(1.23456789) 结果：('1.23457', '1.23456789')
import re
regx=re.compile('(?<![\d.])'
'(?!\d*\.\d*\.)' # excludes certain string as not being numbers
'((\d|\.\d)([\d.])*?)' # the only matching group
'([0\.]*)'
'(?![\d.])')
regx.sub('\\1',ch)
.
John Machin 说 10000 和 10000.000 产生 1 而不是 10000
我在(?!(?<=0)\.)的帮助下更正了替换功能
import re
regx = re.compile('(?<![\d.])' '(?![1-9]\d*(?![\d.])|\d*\.\d*\.)'
'0*(?!(?<=0)\.)'
'([\d.]+?)' # the only group , which is kept
'\.?0*'
'(?![\d.])')
regx.sub('\\1',ch)
.
纠正剩余的缺点 [ '.0000' 产生 '.' ，由 John Machin 指出，'000078000' 产生'78' ] ，我重写了一个基于新想法的正则表达式。它更简单。正则表达式检测所有类型的数字。
此解决方案不仅可以消除尾随零，还可以消除航向零。
这是此解决方案与 John Machin 的 tidy_float() 、samplebias 的 number_format() 、arussell84 的 '{:g}'.format() 的比较。我的函数的结果（这次都正确）与其他函数的结果存在一些差异：
import re
def number_shaver(ch,
regx = re.compile('(?<![\d.])0*(?:'
'(\d+)\.?|\.(0)'
'|(\.\d+?)|(\d+\.\d+?)'
')0*(?![\d.])') ,
repl = lambda mat: mat.group(mat.lastindex)
if mat.lastindex!=3
else '0' + mat.group(3) ):
return regx.sub(repl,ch)
def tidy_float(s): # John Machin
"""Return tidied float representation.
Remove superflous leading/trailing zero digits.
Remove '.' if value is an integer.
Return '****' if float(s) fails.
"""
# float?
try:
f = float(s)
except ValueError:
return s
# int?
try:
i = int(s)
return str(i)
except ValueError:
pass
# scientific notation?
if 'e' in s or 'E' in s:
t = s.lstrip('0')
if t.startswith('.'): t = '0' + t
return t
# float with integral value (includes zero)?
i = int(f)
if i == f:
return str(i)
assert '.' in s
t = s.strip('0')
if t.startswith('.'): t = '0' + t
if t.endswith('.'): t += '0'
return t
def format_float(s): # arrussell84
return '{:g}'.format(float(s)) if s.count('.')<2 \
else "Can't treat"
import decimal
def format_number(num):
try:
dec = decimal.Decimal(num)
except:
return 'bad'
tup = dec.as_tuple()
delta = len(tup.digits) + tup.exponent
digits = ''.join(str(d) for d in tup.digits)
if delta <= 0:
zeros = abs(tup.exponent) - len(tup.digits)
val = '0.' + ('0'*zeros) + digits
else:
val = digits[:delta] + ('0'*tup.exponent) + '.' + digits[delta:]
val = val.rstrip('0')
if val[-1] == '.':
val = val[:-1]
if tup.sign:
return '-' + val
return val
numbers = ['23456000', '23456000.', '23456000.000',
'00023456000', '000023456000.', '000023456000.000',
'10000', '10000.', '10000.000',
'00010000', '00010000.', '00010000.000',
'24', '24.', '24.000',
'00024', '00024.', '00024.000',
'8', '8.', '8.000',
'0008', '0008.', '0008.000',
'0', '00000', '0.', '000.',
'\n',
'0.0', '0.000', '000.0', '000.000', '.000000', '.0',
'\n',
'.00023456', '.00023456000', '.00503', '.00503000',
'.068', '.0680000', '.8', '.8000',
'.123456123456', '.123456123456000',
'.657', '.657000', '.45', '.4500000', '.7', '.70000',
'\n',
'0.0000023230000', '000.0000023230000',
'0.0081000', '0000.0081000',
'0.059000', '0000.059000',
'0.78987400000', '00000.78987400000',
'0.4400000', '00000.4400000',
'0.5000', '0000.5000',
'0.90', '000.90', '0.7', '000.7',
'\n',
'2.6', '00002.6', '00002.60000',
'4.71', '0004.71', '0004.7100',
'23.49', '00023.49', '00023.490000',
'103.45', '0000103.45', '0000103.45000',
'10003.45067', '000010003.45067', '000010003.4506700',
'15000.0012', '000015000.0012', '000015000.0012000',
'78000.89', '000078000.89', '000078000.89000',
'\n',
'.0457e10', '.0457000e10','00000.0457000e10',
'258e8', '2580000e4', '0000000002580000e4',
# notice the difference of exponents
'0.782e10', '0000.782e10', '0000.7820000e10',
'1.23E2', '0001.23E2', '0001.2300000E2',
'432e-102', '0000432e-102', '004320000e-106',
# notice the difference of exponents
'1.46e10', '0001.46e10', '0001.4600000e10',
'1.077e-300', '0001.077e-300', '0001.077000e-300',
'1.069e10', '0001.069e10', '0001.069000e10',
'105040.03e10', '000105040.03e10', '105040.0300e10',
'\n',
'..18000', '25..00', '36...77', '2..8',
'3.8..9', '.12500.', '12.51.400' ]
pat = '%18s %-15s %-15s %-15s %s' li = [pat % ('测试数字','float_shaver', 'tidy_float',"format_number()","'{:g}'.format()")] li.extend(pat % (n,number_shaver(n),tidy_float(n),format_number(n),format_float(n)) if n!='\n' else '\n' for n in numbers)
打印'\n'.join(li)
比较结果：
tested number float_shaver tidy_float format_number() '{:g}'.format()
23456000 23456000 23456000 23456000 2.3456e+07
23456000. 23456000 23456000 23456000 2.3456e+07
23456000.000 23456000 23456000 23456000 2.3456e+07
00023456000 23456000 23456000 23456000 2.3456e+07
000023456000. 23456000 23456000 23456000 2.3456e+07
000023456000.000 23456000 23456000 23456000 2.3456e+07
10000 10000 10000 10000 10000
10000. 10000 10000 10000 10000
10000.000 10000 10000 10000 10000
00010000 10000 10000 10000 10000
00010000. 10000 10000 10000 10000
00010000.000 10000 10000 10000 10000
24 24 24 24 24
24. 24 24 24 24
24.000 24 24 24 24
00024 24 24 24 24
00024. 24 24 24 24
00024.000 24 24 24 24
8 8 8 8 8
8. 8 8 8 8
8.000 8 8 8 8
0008 8 8 8 8
0008. 8 8 8 8
0008.000 8 8 8 8
0 0 0 0 0
00000 0 0 0 0
0. 0 0 0 0
000. 0 0 0 0
0.0 0 0 0 0
0.000 0 0 0 0
000.0 0 0 0 0
000.000 0 0 0 0
.000000 0 0 0 0
.0 0 0 0 0
.00023456 0.00023456 0.00023456 0.00023456 0.00023456
.00023456000 0.00023456 0.00023456 0.00023456 0.00023456
.00503 0.00503 0.00503 0.00503 0.00503
.00503000 0.00503 0.00503 0.00503 0.00503
.068 0.068 0.068 0.068 0.068
.0680000 0.068 0.068 0.068 0.068
.8 0.8 0.8 0.8 0.8
.8000 0.8 0.8 0.8 0.8
.123456123456 0.123456123456 0.123456123456 0.123456123456 0.123456
.123456123456000 0.123456123456 0.123456123456 0.123456123456 0.123456
.657 0.657 0.657 0.657 0.657
.657000 0.657 0.657 0.657 0.657
.45 0.45 0.45 0.45 0.45
.4500000 0.45 0.45 0.45 0.45
.7 0.7 0.7 0.7 0.7
.70000 0.7 0.7 0.7 0.7
0.0000023230000 0.000002323 0.000002323 0.000002323 2.323e-06
000.0000023230000 0.000002323 0.000002323 0.000002323 2.323e-06
0.0081000 0.0081 0.0081 0.0081 0.0081
0000.0081000 0.0081 0.0081 0.0081 0.0081
0.059000 0.059 0.059 0.059 0.059
0000.059000 0.059 0.059 0.059 0.059
0.78987400000 0.789874 0.789874 0.789874 0.789874
00000.78987400000 0.789874 0.789874 0.789874 0.789874
0.4400000 0.44 0.44 0.44 0.44
00000.4400000 0.44 0.44 0.44 0.44
0.5000 0.5 0.5 0.5 0.5
0000.5000 0.5 0.5 0.5 0.5
0.90 0.9 0.9 0.9 0.9
000.90 0.9 0.9 0.9 0.9
0.7 0.7 0.7 0.7 0.7
000.7 0.7 0.7 0.7 0.7
2.6 2.6 2.6 2.6 2.6
00002.6 2.6 2.6 2.6 2.6
00002.60000 2.6 2.6 2.6 2.6
4.71 4.71 4.71 4.71 4.71
0004.71 4.71 4.71 4.71 4.71
0004.7100 4.71 4.71 4.71 4.71
23.49 23.49 23.49 23.49 23.49
00023.49 23.49 23.49 23.49 23.49
00023.490000 23.49 23.49 23.49 23.49
103.45 103.45 103.45 103.45 103.45
0000103.45 103.45 103.45 103.45 103.45
0000103.45000 103.45 103.45 103.45 103.45
10003.45067 10003.45067 10003.45067 10003.45067 10003.5
000010003.45067 10003.45067 10003.45067 10003.45067 10003.5
000010003.4506700 10003.45067 10003.45067 10003.45067 10003.5
15000.0012 15000.0012 15000.0012 15000.0012 15000
000015000.0012 15000.0012 15000.0012 15000.0012 15000
000015000.0012000 15000.0012 15000.0012 15000.0012 15000
78000.89 78000.89 78000.89 78000.89 78000.9
000078000.89 78000.89 78000.89 78000.89 78000.9
000078000.89000 78000.89 78000.89 78000.89 78000.9
.0457e10 0.0457e10 0.0457e10 457000000 4.57e+08
.0457000e10 0.0457e10 0.0457000e10 457000000 4.57e+08
00000.0457000e10 0.0457e10 0.0457000e10 457000000 4.57e+08
258e8 258e8 258e8 25800000000 2.58e+10
2580000e4 2580000e4 2580000e4 25800000000 2.58e+10
0000000002580000e4 2580000e4 2580000e4 25800000000 2.58e+10
0.782e10 0.782e10 0.782e10 7820000000 7.82e+09
0000.782e10 0.782e10 0.782e10 7820000000 7.82e+09
0000.7820000e10 0.782e10 0.7820000e10 7820000000 7.82e+09
1.23E2 1.23E2 1.23E2 123 123
0001.23E2 1.23E2 1.23E2 123 123
0001.2300000E2 1.23E2 1.2300000E2 123 123
432e-102 432e-102 432e-102 0.000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000432 4.32e-100
0000432e-102 432e-102 432e-102 0.000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000432 4.32e-100
004320000e-106 4320000e-106 4320000e-106 0.000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000432 4.32e-100
1.46e10 1.46e10 1.46e10 14600000000 1.46e+10
0001.46e10 1.46e10 1.46e10 14600000000 1.46e+10
0001.4600000e10 1.46e10 1.4600000e10 14600000000 1.46e+10
1.077e-300 1.077e-300 1.077e-300 0.000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001077 1.077e-300
0001.077e-300 1.077e-300 1.077e-300 0.000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001077 1.077e-300
0001.077000e-300 1.077e-300 1.077000e-300 0.000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001077 1.077e-300
1.069e10 1.069e10 1.069e10 10690000000 1.069e+10
0001.069e10 1.069e10 1.069e10 10690000000 1.069e+10
0001.069000e10 1.069e10 1.069000e10 10690000000 1.069e+10
105040.03e10 105040.03e10 105040.03e10 1050400300000000 1.0504e+15
000105040.03e10 105040.03e10 105040.03e10 1050400300000000 1.0504e+15
105040.0300e10 105040.03e10 105040.0300e10 1050400300000000 1.0504e+15
..18000 ..18000 ..18000 bad Can't treat
25..00 25..00 25..00 bad Can't treat
36...77 36...77 36...77 bad Can't treat
2..8 2..8 2..8 bad Can't treat
3.8..9 3.8..9 3.8..9 bad Can't treat
.12500. .12500. .12500. bad Can't treat
12.51.400 12.51.400 12.51.400 bad Can't treat
.
我认为我的解决方案有两个优点：
正则表达式和函数 number_shave() 都很短
number_shave() 不仅一次只处理一个数字，而且还检测并处理字符串中的所有数字。这是 John Machin 和 arrussel84 的解决方案无法解决的问题：
代码：
numbers = [['', '23456000', '23456000.', '23456000.000 \n',
'00023456000', '000023456000.', '000023456000.000 \n',
'10000', '10000.', '10000.000 \n',
'00010000', '00010000.', '00010000.000 \n',
'24', '24.', '24.000 \n',
'00024', '00024.', '00024.000 \n',
'8', '8.', '8.000 \n',
'0008', '0008.', '0008.000 \n',
'0', '00000', '0.', '000.' ],
['0.0', '0.000', '000.0', '000.000', '.000000', '.0'],
['.00023456', '.00023456000', '.00503', '.00503000 \n',
'.068', '.0680000', '.8', '.8000 \n',
'.123456123456', '.123456123456000 \n',
'.657', '.657000', '.45', '.4500000', '.7', '.70000'],
['0.0000023230000', '000.0000023230000 \n',
'0.0081000', '0000.0081000 \n',
'0.059000', '0000.059000 \n',
'0.78987400000', '00000.78987400000 \n',
'0.4400000', '00000.4400000 \n',
'0.5000', '0000.5000 \n',
'0.90', '000.90', '0.7', '000.7 '],
['2.6', '00002.6', '00002.60000 \n',
'4.71', '0004.71', '0004.7100 \n',
'23.49', '00023.49', '00023.490000 \n',
'103.45', '0000103.45', '0000103.45000 \n',
'10003.45067', '000010003.45067', '000010003.4506700 \n',
'15000.0012', '000015000.0012', '000015000.0012000 \n',
'78000.89', '000078000.89', '000078000.89000'],
['.0457e10', '.0457000e10 \n',
'0.782e10', '0000.782e10', '0000.7820000e10 \n',
'1.23E2', '0001.23E2', '0001.2300000E2 \n',
'1.46e10', '0001.46e10', '0001.4600000e10 \n',
'1.077e-456', '0001.077e-456', '0001.077000e-456 \n',
'1.069e10', '0001.069e10', '0001.069000e10 \n',
'105040.03e10', '000105040.03e10', '105040.03e10'],
['..18000', '25..00', '36...77', '2..8 \n',
'3.8..9', '.12500.', '12.51.400' ]]
import re
def number_shaver(ch,
regx = re.compile('(?<![\d.])0*(?:'
'(\d+)\.?|\.(0)'
'|(\.\d+?)|(\d+\.\d+?)'
')0*(?![\d.])') ,
repl = lambda mat: mat.group(mat.lastindex)
if mat.lastindex!=3
else '0' + mat.group(3) ):
return regx.sub(repl,ch)
for li in numbers:
one_string = ' --- '.join(li)
print one_string + '\n\n' + number_shaver(one_string) + \
'\n\n' + 3*'---------------------' + '\n'
包含多个数字的字符串的处理结果：
--- 23456000 --- 23456000. --- 23456000.000
--- 00023456000 --- 000023456000. --- 000023456000.000
--- 10000 --- 10000. --- 10000.000
--- 00010000 --- 00010000. --- 00010000.000
--- 24 --- 24. --- 24.000
--- 00024 --- 00024. --- 00024.000
--- 8 --- 8. --- 8.000
--- 0008 --- 0008. --- 0008.000
--- 0 --- 00000 --- 0. --- 000.
--- 23456000 --- 23456000 --- 23456000
--- 23456000 --- 23456000 --- 23456000
--- 10000 --- 10000 --- 10000
--- 10000 --- 10000 --- 10000
--- 24 --- 24 --- 24
--- 24 --- 24 --- 24
--- 8 --- 8 --- 8
--- 8 --- 8 --- 8
--- 0 --- 0 --- 0 --- 0
---------------------------------------------------------------
0.0 --- 0.000 --- 000.0 --- 000.000 --- .000000 --- .0
0 --- 0 --- 0 --- 0 --- 0 --- 0
---------------------------------------------------------------
.00023456 --- .00023456000 --- .00503 --- .00503000
--- .068 --- .0680000 --- .8 --- .8000
--- .123456123456 --- .123456123456000
--- .657 --- .657000 --- .45 --- .4500000 --- .7 --- .70000
0.00023456 --- 0.00023456 --- 0.00503 --- 0.00503
--- 0.068 --- 0.068 --- 0.8 --- 0.8
--- 0.123456123456 --- 0.123456123456
--- 0.657 --- 0.657 --- 0.45 --- 0.45 --- 0.7 --- 0.7
---------------------------------------------------------------
0.0000023230000 --- 000.0000023230000
--- 0.0081000 --- 0000.0081000
--- 0.059000 --- 0000.059000
--- 0.78987400000 --- 00000.78987400000
--- 0.4400000 --- 00000.4400000
--- 0.5000 --- 0000.5000
--- 0.90 --- 000.90 --- 0.7 --- 000.7
0.000002323 --- 0.000002323
--- 0.0081 --- 0.0081
--- 0.059 --- 0.059
--- 0.789874 --- 0.789874
--- 0.44 --- 0.44
--- 0.5 --- 0.5
--- 0.9 --- 0.9 --- 0.7 --- 0.7
---------------------------------------------------------------
2.6 --- 00002.6 --- 00002.60000
--- 4.71 --- 0004.71 --- 0004.7100
--- 23.49 --- 00023.49 --- 00023.490000
--- 103.45 --- 0000103.45 --- 0000103.45000
--- 10003.45067 --- 000010003.45067 --- 000010003.4506700
--- 15000.0012 --- 000015000.0012 --- 000015000.0012000
--- 78000.89 --- 000078000.89 --- 000078000.89000
2.6 --- 2.6 --- 2.6
--- 4.71 --- 4.71 --- 4.71
--- 23.49 --- 23.49 --- 23.49
--- 103.45 --- 103.45 --- 103.45
--- 10003.45067 --- 10003.45067 --- 10003.45067
--- 15000.0012 --- 15000.0012 --- 15000.0012
--- 78000.89 --- 78000.89 --- 78000.89
---------------------------------------------------------------
.0457e10 --- .0457000e10
--- 0.782e10 --- 0000.782e10 --- 0000.7820000e10
--- 1.23E2 --- 0001.23E2 --- 0001.2300000E2
--- 1.46e10 --- 0001.46e10 --- 0001.4600000e10
--- 1.077e-456 --- 0001.077e-456 --- 0001.077000e-456
--- 1.069e10 --- 0001.069e10 --- 0001.069000e10
--- 105040.03e10 --- 000105040.03e10 --- 105040.03e10
0.0457e10 --- 0.0457e10
--- 0.782e10 --- 0.782e10 --- 0.782e10
--- 1.23E2 --- 1.23E2 --- 1.23E2
--- 1.46e10 --- 1.46e10 --- 1.46e10
--- 1.077e-456 --- 1.077e-456 --- 1.077e-456
--- 1.069e10 --- 1.069e10 --- 1.069e10
--- 105040.03e10 --- 105040.03e10 --- 105040.03e10
---------------------------------------------------------------
..18000 --- 25..00 --- 36...77 --- 2..8
--- 3.8..9 --- .12500. --- 12.51.400
..18000 --- 25..00 --- 36...77 --- 2..8
--- 3.8..9 --- .12500. --- 12.51.400
---------------------------------------------------------------
.
因此，正则表达式也可用于仅查找字符串中的所有数字，而不需要删除零。
.
PS：在我解释正则表达式及其功能的其他答案中查看更多信息
【讨论】：
'.0000' 产生 '.'
'.0000' 产生 '.' ，因为程序将诸如 '.657000' 之类的数字更改为 '.657' 。我想更正这个特定的结果，因为它是 '.0000' 的缺点，并且对于 '.657' 不好看，我也更喜欢 '0.657'。该代码还给出了另一个错误结果：'000078000' is changed to '78'
脚本：
def tidy_float(s):
"""Return tidied float representation.
Remove superflous leading/trailing zero digits.
Remove '.' if value is an integer.
Return '****' if float(s) fails.
"""
# float?
try:
f = float(s)
except ValueError:
return '****'
# int?
try:
i = int(s)
return str(i)
except ValueError:
pass
# scientific notation?
if 'e' in s or 'E' in s:
t = s.lstrip('0')
if t.startswith('.'): t = '0' + t
return t
# float with integral value (includes zero)?
i = int(f)
if i == f:
return str(i)
assert '.' in s
t = s.strip('0')
if t.startswith('.'): t = '0' + t
if t.endswith('.'): t += '0'
return t
if __name__ == "__main__":
# Each line has test string followed by expected output
tests = """
0.000 0
0 0
0000 0
0.4000 0.4
0.0081000 0.0081
103.45 103.45
103.4506700 103.45067
14500.0012 14500.0012
478000.89 478000.89
993.59.18 ****
12.5831.400 ****
.458 0.458
.48587000 0.48587
.0000 0
10000 10000
10000.000 10000
-10000 -10000
-10000.000 -10000
1.23e2 1.23e2
1.23e10 1.23e10
.123e10 0.123e10
""".splitlines()
for test in tests:
x = test.split()
if not x: continue
data, expected = x
actual = tidy_float(data)
print "data=%r exp=%r act=%r %s" % (
data, expected, actual, ["**FAIL**", ""][actual == expected])
输出（Python 2.7.1）：
data='0.000' exp='0' act='0'
data='0' exp='0' act='0'
data='0000' exp='0' act='0'
data='0.4000' exp='0.4' act='0.4'
data='0.0081000' exp='0.0081' act='0.0081'
data='103.45' exp='103.45' act='103.45'
data='103.4506700' exp='103.45067' act='103.45067'
data='14500.0012' exp='14500.0012' act='14500.0012'
data='478000.89' exp='478000.89' act='478000.89'
data='993.59.18' exp='****' act='****'
data='12.5831.400' exp='****' act='****'
data='.458' exp='0.458' act='0.458'
data='.48587000' exp='0.48587' act='0.48587'
data='.0000' exp='0' act='0'
data='10000' exp='10000' act='10000'
data='10000.000' exp='10000' act='10000'
data='-10000' exp='-10000' act='-10000'
data='-10000.000' exp='-10000' act='-10000'
data='1.23e2' exp='1.23e2' act='1.23e2'
data='1.23e10' exp='1.23e10' act='1.23e10'
data='.123e10' exp='0.123e10' act='0.123e10'
【讨论】：
tidy_float() 为 .0457000e10 返回 0.0457000e10 ，为 0001.077000e-456 返回 1.077000e-456 等
（所有人都渴望只在一篇文章中）
正则表达式的模式定义了 4 个子模式，每个子模式都与特定类型的数字匹配。每次正则表达式与字符串的一部分匹配时，只有一个子模式匹配，因此可以在替换函数中使用 mat.lastindex。以下代码显示了子模式与各种数字的匹配：
import re
def float_show(ch,
regx = re.compile(
'(?<![\d.])'
'0*' # potentiel heading zeros
'(?:'
'(\d+)\.?' # INTEGERS :
# ~ pure integers non-0 or 0
# 000450 , 136000 , 87 , 000 , 0
# ~ integer part non-0 + '.'
# 0044. , 4100.
# ~ integer part 0 + '.'
# 000. , 0.
# ~ integer part non-0 + '.' + fractional part 0:
# 000570.00 , 193.0 , 3.000
'|\.(0)' # SPECIAL CASE, 0 WITH FRACTIONAL PART :
# ~ integer part 0 + compulsory fractional part 0:
# 000.0, 0.000 , .0 , .00000
'|(\.\d+?)' # FLOATING POINT NUMBER
# ~ with integer part 0:
# 000.0890 , 0.52 , 0.1 , .077000 , .1400 , .0006010
'|(\d+\.\d+?)' # FLOATING POINT NUMBER
# ~ with integer part non-0:
# 0024000.013000 , 145.0235 , 3.00058
')'
'0*' # potential tailing zeros
'(?![\d.])'),
repl = lambda mat: mat.group(mat.lastindex)
if mat.lastindex!=3
else '0' + mat.group(3) ):
mat = regx.search(ch)
if mat:
return (ch,regx.sub(repl,ch),repr(mat.groups()))
else:
return (ch,'No match','No groups')
numbers = ['23456000', '23456000.', '23456000.000',
'00023456000', '000023456000.', '000023456000.000',
'10000', '10000.', '10000.000',
'00010000', '00010000.', '00010000.000',
'24', '24.', '24.000',
'00024', '00024.', '00024.000',
'8', '8.', '8.000',
'0008', '0008.', '0008.000',
'0', '00000', '0.', '000.',
'\n',
'0.0', '0.000', '000.0', '000.000', '.000000', '.0',
'\n',
'.00023456', '.00023456000', '.00503', '.00503000',
'.068', '.0680000', '.8', '.8000',
'.123456123456', '.123456123456000',
'.657', '.657000', '.45', '.4500000', '.7', '.70000',
'\n',
'0.0000023230000', '000.0000023230000',
'0.0081000', '0000.0081000',
'0.059000', '0000.059000',
'0.78987400000', '00000.78987400000',
'0.4400000', '00000.4400000',
'0.5000', '0000.5000',
'0.90', '000.90', '0.7', '000.7',
'\n',
'2.6', '00002.6', '00002.60000',
'4.71', '0004.71', '0004.7100',
'23.49', '00023.49', '00023.490000',
'103.45', '0000103.45', '0000103.45000',
'10003.45067', '000010003.45067', '000010003.4506700',
'15000.0012', '000015000.0012', '000015000.0012000',
'78000.89', '000078000.89', '000078000.89000',
'\n',
'.0457e10', '.0457000e10',
'0.782e10', '0000.782e10', '0000.7820000e10',
'1.23E2', '0001.23E2', '0001.2300000E2',
'1.46e10', '0001.46e10', '0001.4600000e10',
'1.077e-456', '0001.077e-456', '0001.077000e-456',
'1.069e10', '0001.069e10', '0001.069000e10',
'105040.03e10', '000105040.03e10', '105040.0300e10',
'\n',
'..18000', '25..00', '36...77', '2..8',
'3.8..9', '.12500.', '12.51.400' ]
pat = '%20s %-16s %s'
li = [pat % ('tested number ',' shaved float',' regx.search(number).groups()')]
li.extend(pat % float_show(ch) if ch!='\n' else '\n' for ch in numbers)
print '\n'.join(li)
展示
tested number shaved float regx.search(number).groups()
23456000 23456000 ('23456000', None, None, None)
23456000. 23456000 ('23456000', None, None, None)
23456000.000 23456000 ('23456000', None, None, None)
00023456000 23456000 ('23456000', None, None, None)
000023456000. 23456000 ('23456000', None, None, None)
000023456000.000 23456000 ('23456000', None, None, None)
10000 10000 ('10000', None, None, None)
10000. 10000 ('10000', None, None, None)
10000.000 10000 ('10000', None, None, None)
00010000 10000 ('10000', None, None, None)
00010000. 10000 ('10000', None, None, None)
00010000.000 10000 ('10000', None, None, None)
24 24 ('24', None, None, None)
24. 24 ('24', None, None, None)
24.000 24 ('24', None, None, None)
00024 24 ('24', None, None, None)
00024. 24 ('24', None, None, None)
00024.000 24 ('24', None, None, None)
8 8 ('8', None, None, None)
8. 8 ('8', None, None, None)
8.000 8 ('8', None, None, None)
0008 8 ('8', None, None, None)
0008. 8 ('8', None, None, None)
0008.000 8 ('8', None, None, None)
0 0 ('0', None, None, None)
00000 0 ('0', None, None, None)
0. 0 ('0', None, None, None)
000. 0 ('0', None, None, None)
0.0 0 (None, '0', None, None)
0.000 0 (None, '0', None, None)
000.0 0 (None, '0', None, None)
000.000 0 (None, '0', None, None)
.000000 0 (None, '0', None, None)
.0 0 (None, '0', None, None)
.00023456 0.00023456 (None, None, '.00023456', None)
.00023456000 0.00023456 (None, None, '.00023456', None)
.00503 0.00503 (None, None, '.00503', None)
.00503000 0.00503 (None, None, '.00503', None)
.068 0.068 (None, None, '.068', None)
.0680000 0.068 (None, None, '.068', None)
.8 0.8 (None, None, '.8', None)
.8000 0.8 (None, None, '.8', None)
.123456123456 0.123456123456 (None, None, '.123456123456', None)
.123456123456000 0.123456123456 (None, None, '.123456123456', None)
.657 0.657 (None, None, '.657', None)
.657000 0.657 (None, None, '.657', None)
.45 0.45 (None, None, '.45', None)
.4500000 0.45 (None, None, '.45', None)
.7 0.7 (None, None, '.7', None)
.70000 0.7 (None, None, '.7', None)
0.0000023230000 0.000002323 (None, None, '.000002323', None)
000.0000023230000 0.000002323 (None, None, '.000002323', None)
0.0081000 0.0081 (None, None, '.0081', None)
0000.0081000 0.0081 (None, None, '.0081', None)
0.059000 0.059 (None, None, '.059', None)
0000.059000 0.059 (None, None, '.059', None)
0.78987400000 0.789874 (None, None, '.789874', None)
00000.78987400000 0.789874 (None, None, '.789874', None)
0.4400000 0.44 (None, None, '.44', None)
00000.4400000 0.44 (None, None, '.44', None)
0.5000 0.5 (None, None, '.5', None)
0000.5000 0.5 (None, None, '.5', None)
0.90 0.9 (None, None, '.9', None)
000.90 0.9 (None, None, '.9', None)
0.7 0.7 (None, None, '.7', None)
000.7 0.7 (None, None, '.7', None)
2.6 2.6 (None, None, None, '2.6')
00002.6 2.6 (None, None, None, '2.6')
00002.60000 2.6 (None, None, None, '2.6')
4.71 4.71 (None, None, None, '4.71')
0004.71 4.71 (None, None, None, '4.71')
0004.7100 4.71 (None, None, None, '4.71')
23.49 23.49 (None, None, None, '23.49')
00023.49 23.49 (None, None, None, '23.49')
00023.490000 23.49 (None, None, None, '23.49')
103.45 103.45 (None, None, None, '103.45')
0000103.45 103.45 (None, None, None, '103.45')
0000103.45000 103.45 (None, None, None, '103.45')
10003.45067 10003.45067 (None, None, None, '10003.45067')
000010003.45067 10003.45067 (None, None, None, '10003.45067')
000010003.4506700 10003.45067 (None, None, None, '10003.45067')
15000.0012 15000.0012 (None, None, None, '15000.0012')
000015000.0012 15000.0012 (None, None, None, '15000.0012')
000015000.0012000 15000.0012 (None, None, None, '15000.0012')
78000.89 78000.89 (None, None, None, '78000.89')
000078000.89 78000.89 (None, None, None, '78000.89')
000078000.89000 78000.89 (None, None, None, '78000.89')
.0457e10 0.0457e10 (None, None, '.0457', None)
.0457000e10 0.0457e10 (None, None, '.0457', None)
0.782e10 0.782e10 (None, None, '.782', None)
0000.782e10 0.782e10 (None, None, '.782', None)
0000.7820000e10 0.782e10 (None, None, '.782', None)
1.23E2 1.23E2 (None, None, None, '1.23')
0001.23E2 1.23E2 (None, None, None, '1.23')
0001.2300000E2 1.23E2 (None, None, None, '1.23')
1.46e10 1.46e10 (None, None, None, '1.46')
0001.46e10 1.46e10 (None, None, None, '1.46')
0001.4600000e10 1.46e10 (None, None, None, '1.46')
1.077e-456 1.077e-456 (None, None, None, '1.077')
0001.077e-456 1.077e-456 (None, None, None, '1.077')
0001.077000e-456 1.077e-456 (None, None, None, '1.077')
1.069e10 1.069e10 (None, None, None, '1.069')
0001.069e10 1.069e10 (None, None, None, '1.069')
0001.069000e10 1.069e10 (None, None, None, '1.069')
105040.03e10 105040.03e10 (None, None, None, '105040.03')
000105040.03e10 105040.03e10 (None, None, None, '105040.03')
105040.0300e10 105040.03e10 (None, None, None, '105040.03')
..18000 No match No groups
25..00 No match No groups
36...77 No match No groups
2..8 No match No groups
3.8..9 No match No groups
.12500. No match No groups
12.51.400 No match No groups
【讨论】：