Implement a kwargs converter to take a list and create multiple "-Bla" entries

[leouieda]

Some arguments are meant to be passed twice, for example -I1/1p,blue -I2/0.25p,blue. This can't happen in Python. The way to fix this is to add a converter to kwargs_to_strings in gmt/utils.py that takes a list (I=['1/1p,blue', '2/0.25p,blue']) and creates multiple entries in the argument list.

[seisman]

Two possible ways to fix this issue:

1. Add another conversion (for example multi_entries) in kwargs_to_string and convert keywords argument {'I': ['1/1p,blue', '2/0.25p,blue']} to string -I1/1p,blue -I2/0.25p,blue. Meanwhile delete {'I': ['1/1p,blue', '2/0.25p,blue']} from **kwargs and append -I1/1p,blue -I2/0.25p,blue to *args.

2. Do nothing in kwargs_to_strings but do the conversion in build_arg_string. If the value of a argument is a list, then convert it multiple times (from {'I': ['1/1p,blue', '2/0.25p,blue']} to -I1/1p,blue -I2/0.25p,blue).

Which one do you prefer?

[leouieda]

It would fit better in kwargs_to_string but that won't work because we can't have multiple I entries in a dict. So it's better to do this in build_arg_string. You can use is_nonstr_iter to check and then make multiple entries. Thanks for taking a look at this.

For arguments like -B, I'm thinking of making Bx and By separate arguments with their own aliases framex, framey. But for some, like the -I example, this doesn't work.