Hi i am reading a source and it has a line:
fn = 'total-listmix-{}-{}.xml'.format(opt.os, opt.compiler)
exept Exception as e:
raise Exception('error merging coverage: {}'.format(e))
I think the {} mean a dict but i do not understand what dict here ? Is is a dict took from format ?
The {} is a replacement field, not a dict. This is mentioned in the Python Documentation:
Format strings contain “replacement fields” surrounded by curly braces
{}. Anything that is not contained in braces is considered literal text, which is copied unchanged to the output. If you need to include a brace character in the literal text, it can be escaped by doubling:{{and}}.
One simple example is:
name = "Tom"
print("Hello, {}".format(name)) # prints "Hello, Tom"
Here are a few more examples from the Python Documentation:
"First, thou shalt count to {0}" # References first positional argument
"Bring me a {}" # Implicitly references the first positional argument
"From {} to {}" # Same as "From {0} to {1}"
"My quest is {name}" # References keyword argument 'name'
"Weight in tons {0.weight}" # 'weight' attribute of first positional arg
"Units destroyed: {players[0]}" # First element of keyword argument 'players'.
And this is the grammar of the replacement field:
replacement_field ::= "{" [field_name] ["!" conversion] [":" format_spec] "}"
field_name ::= arg_name ("." attribute_name | "[" element_index "]")*
arg_name ::= [identifier | digit+]
attribute_name ::= identifier
element_index ::= digit+ | index_string
index_string ::= <any source character except "]"> +
conversion ::= "r" | "s" | "a"
format_spec ::= <described in the next section>
