如何使 Python 格式浮动一定数量的有效数字？
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How to make Python format floats with certain amount of significant digits?
提问by user1145925
I want my Python (2.4.3) output numbers to have a certain format. Specifically, if the number is a terminating decimal with <= 6 significant digits, show it all. However, if it has > 6 significant digits, then output only 6 significant digits.
我希望我的 Python (2.4.3) 输出数字具有某种格式。具体来说，如果数字是 <= 6 位有效数字的终止小数，则全部显示。但是，如果它有 > 6 个有效数字，则只输出 6 个有效数字。
"A" shows how Python is writing the floats. "B" shows how I want them written. How can I make Python format my numbers in that way?
“A”显示 Python 如何编写浮点数。“B”显示了我希望它们的书写方式。如何让 Python 以这种方式格式化我的数字？
A:
10188469102.605597
5.5657188485
3.539
22.1522612479
0
15.9638450858
0.284024
7.58096703786
24.3469152383
B:
1.01885e+10
5.56572
3.539
22.1523
0
15.9638
0.284024
7.58097
24.3469
采纳答案by Joachim Isaksson
You'll want the gmodifier for formatthat drops insignificant zeroes;
您将需要g用于format删除无关紧要的零的修饰符；
>>> "{0:.6g}".format(5.5657188485)
'5.56572'
>>> "{0:.6g}".format(3.539)
'3.539'
Sorry, my update also includes the fact that I am restricted to using Python 2.4.3, which does not have format() function.
抱歉，我的更新还包括我只能使用没有 format() 函数的 Python 2.4.3。
The format specifiers work even without the .format()function:
即使没有.format()函数，格式说明符也能工作：
>>> for i in a:
... print '%.6g' % (i,)
...
1.01885e+10
5.56572
3.539
22.1523
0
15.9638
0.284024
7.58097
24.3469
回答by sundar nataraj
try this way
试试这个方法
a=[10188469102.605597,5.5657188485,3.539,22.1522612479,0,15.9638450858,0.284024,7.58096703786,24.3469152383]
for i in a:
if i >100:
print '{:.6e}'.format(i)
else:
print '{:.6f}'.format(i)
for lower version of python
对于较低版本的python
for i in a:
if i >100:
print '%6e'%i
else:
print '%6f'%i
output
输出
1.018847e+10
5.565719
3.539000
22.152261
0.000000
15.963845
0.284024
7.580967
24.346915
回答by jadelord
There is a way to retain trailing zerosso that it consistently shows the number of significant digits. Not exactly what OP wanted, but probably useful to many.
有一种方法可以保留尾随零，以便始终显示有效数字的数量。不完全是 OP 想要的，但可能对许多人有用。
a = [10188469102.605597,5.5657188485,3.539,22.1522612479,0,15.9638450858,0.284024,7.58096703786,24.3469152383]
for i in a:
print("{:#.6g}".format(i))
Output
输出
1.01885e+10
5.56572
3.53900
22.1523
0.00000
15.9638
0.284024
7.58097
24.3469
Note that this will only work with the formatfunction and not with %operator.
请注意，这仅适用于format函数而不适用于%运算符。
Reference: an undocumented feature (as of 2019)
参考：一个未记录的功能（截至 2019 年）
