String formatting error for arg in dictionary for use in mel.eval

[kiteh]

Hi all, I am trying to do a string formatting in which it is in a dictionary format that is to be used in mel command.

This is my mel command - `mel.eval('animLayerMerge{"BaseAnimation", "my_layer"}')`

In my python format, I rewrote as this:

my_naming = 'my_layer'
command = '"{"BaseAnimation", "{0}"'.format(my_naming)

However this will results in the following error:

# Error: "BaseAnimation", "{0}"
# Traceback (most recent call last):
#   File "<maya console>", line 2, in <module>
# KeyError: '"BaseAnimation", "{0}"' #

No matter how I wrote my `.format`, it will definitely errors out as soon as I tried to incorporate in `{ {0} }` and the reason I am doing this is because I would not want to hardcode the value of `my_naming` as it reads from a text field which would means different naming.

Is there a better way that I can perhaps get around this?

[kiteh]

Adding on, if I tried using `mel.eval('animLayerMerge{"BaseAnimation", "%s"}' % my_naming)`, while it seems to work, but it mutes out my_layer and instead creates another animation layer called `Merged_Layer`

[Robert White]

Try:

my_naming = 'my_layer'
command = '"{{"BaseAnimation", "{0}"'.format(my_naming)

I believe the problem is that because you've got the single open { the formatting code gets confused. To insert a { into a formatted string you just double them up.

[Justin Israel]

https://docs.python.org/2/library/string.html#format-string-syntax

"If you need to include a brace character in the literal text, it can be escaped by doubling: {{ and }}."

Also it seems like you have a typo in your example where you have an extra leading double quote character which would be a syntax error. So I'm assuming that wasn't intentional. 

I would expect it to be like:

my_naming = 'my_layer'

command = '{{"BaseAnimation", "{0}"}} '.format(my_naming)

And I would think the Mel command would be like:

animLayerMerge({...}) 

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[kiteh]

Got it, thank you so much all!

I wasn't aware of the double curly brackets for such scenarios. Thanks again!