python-用字典条目替换字符串条目

Question

I have a string like 'MATERIAL 4 {clad-den} {clad-temp} 2' , and I want to replace entries like {clad-den} , {clad-temp} (in figure brackets) with corresponding values from a dictionary, which have the same key, as enclosed in brackets - like data['clad-den'] to receive a string like: 'MATERIAL 4 6.55 578.0 2' . How can I do that?

I have some thoughts directed at re.sub . Something like: re.sub(('{\\S+}'),data[('\\S+')],string) , but I don't know how to make it use the same key as it's replacing each time.

Answer 1

You can use str.format() out of the box for this:

'MATERIAL 4 {clad-den} {clad-temp} 2'.format(**data)

This will look up clad-den and clad-temp as keys in the data dictionary:

>>> data = {'clad-den': 6.55, 'clad-temp': 578.0}
>>> 'MATERIAL 4 {clad-den} {clad-temp} 2'.format(**data)
'MATERIAL 4 6.55 578.0 2'

You can do it with re.sub() too, using a function for the replacement parameter:

re.sub(r'{([^{}]+)}', lambda m: str(data[m.group(1)]), template_text)

but this doesn't offer the same flexibility and power that string formatting can offer.