Sorting a list of string in python such that a specific string, if present appears first

Question

I am new to python and hoping that someone can help me out with this. I need to sort a list of strings :

s = ['status', 'value', 'place', 'tag']

I need to sort in such a way that the sorted list looks like this :

s_sorted = ['tag', 'place', 'status', 'value']

In order words, the specific string 'tag' needs to be always in front and the rest of the strings are going to be sorted. I was trying to come up with a comparator that will allow me to do so. But I haven't been able to do that so far. If anyone has experience solving problem like this, I would appreciate if you can share some thoughts.

Answer 1

s = ['status', 'value', 'place', 'tag']
s_sorted = sorted(s, key=lambda x:(x!='tag', x))

The key generates a tuple, with first element boolean of if the element isn't 'tag'. sort sorts by the first element, then the second. This way tag always comes first because False sorts before True.

In the case of the remaining elements - not equal to 'tag' - sorting is done normally on the second tuple element, which is a lexicographical string sort on the value itself.

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From the sorted documentation:

key specifies a function of one argument that is used to extract a comparison key from each list element: key=str.lower. The default value is None (compare the elements directly).