如何在图例标签中使用字符串格式语法

Question

Using Python and Pyplot, one of my plot labels was the following, which gave what I wanted.

plt.ylabel('$\mathrm{\dot{\nu}}$ ($\mathrm{10^{-16} s^{-2}}$)', fontsize=16)

Then instead of the label saying 10^-16, I wanted the label to be 10^-"power" where power is a variable that I have in my code.

I adjusted the code to:

plt.ylabel('$\mathrm{\dot{\nu}}$ ($\mathrm{10^{-{0}} s^{-2}}$)'.format(power), fontsize=16

But I get the following error:

KeyError: '\\dot{\\nu}'

The error seems like it doesn't know when I want to substitute "power" because of all the curly brackets, but I'm not sure how to fix it.

Answer 1

You need to escape all { chars— .format() treats them as special:

>>> '{0}'.format('foo')
'foo'
>>>
'{{{0}}}'.format('foo')  # => '{foo}'
'{foo}'

or

>>> power = 3
>>> '$\mathrm{{\dot{{\nu}}}}$ ($\mathrm{{10^{{-{0}}} s^{{-2}}}}$)'.format(power)
'$\\mathrm{\\dot{\nu}}$ ($\\mathrm{10^{-3} s^{-2}}$)'

Answer 2

You can bypass all of this using the old format syntax:

>>> "%d, %d, %d" % (2, 2 ,4)
'2, 2, 4'
>>> 

In your case:

>>> '$\mathrm{{\dot{{\nu}}}}$ ($\mathrm{{10^{{-%d}} s^{{-2}}}}$)' % 2
'$\\mathrm{{\\dot{{\nu}}}}$ ($\\mathrm{{10^{{-2}} s^{{-2}}}}$)'
>>> 

Using strings:

>>> "%s world" % ('hello')
'hello world'
>>> 

Answer 3

您需要像这样在格式字符串中转义{和} ：

'$\mathrm{{\dot{{\nu}}}}$ ($\mathrm{{10^{{-{0}}} s^{{-2}}}}$)'