If you have Python 2.6 or newer, use format:
'{0:.3g}'.format(num)
For Python 2.5 or older:
'%.3g'%(num)
Explanation:
{0}tells format to print the first argument -- in this case, num.
Everything after the colon (:) specifies the format_spec.
.3 sets the precision to 3.
g removes insignificant zeros. See
http://en.wikipedia.org/wiki/Printf#fprintf
For example:
tests=[(1.00, '1'),
(1.2, '1.2'),
(1.23, '1.23'),
(1.234, '1.23'),
(1.2345, '1.23')]
for num, answer in tests:
result = '{0:.3g}'.format(num)
if result != answer:
print('Error: {0} --> {1} != {2}'.format(num, result, answer))
exit()
else:
print('{0} --> {1}'.format(num,result))
yields
1.0 --> 1
1.2 --> 1.2
1.23 --> 1.23
1.234 --> 1.23
1.2345 --> 1.23
Using Python 3.6 or newer, you could use f-strings:
In [40]: num = 1.234; f'{num:.3g}'
Out[40]: '1.23'
Just use Python's standard string formatting methods:
>>> "{0:.2}".format(1.234232)
'1.2'
>>> "{0:.3}".format(1.234232)
'1.23'
If you are using a Python version under 2.6, use
>>> "%f" % 1.32423
'1.324230'
>>> "%.2f" % 1.32423
'1.32'
>>> "%d" % 1.32423
'1'
Here's a function that will do the trick:
def myformat(x):
return ('%.2f' % x).rstrip('0').rstrip('.')
And here are your examples:
>>> myformat(1.00)
'1'
>>> myformat(1.20)
'1.2'
>>> myformat(1.23)
'1.23'
>>> myformat(1.234)
'1.23'
>>> myformat(1.2345)
'1.23'
Edit:
From looking at other people's answers and experimenting, I found that g does all of the stripping stuff for you. So,
'%.3g' % x
works splendidly too and is slightly different from what other people are suggesting (using '{0:.3}'.format() stuff). I guess take your pick.
Only first part of Justin's answer is correct. Using "%.3g" will not work for all cases as .3 is not the precision, but total number of digits. Try it for numbers like 1000.123 and it breaks.
So, I would use what Justin is suggesting:
>>> ('%.4f' % 12340.123456).rstrip('0').rstrip('.')
'12340.1235'
>>> ('%.4f' % -400).rstrip('0').rstrip('.')
'-400'
>>> ('%.4f' % 0).rstrip('0').rstrip('.')
'0'
>>> ('%.4f' % .1).rstrip('0').rstrip('.')
'0.1'
Source: Stackoverflow.com