It sometimes reverse when I turn a string into a set-CodePudding

The string is: x = 'ABBA'

whenever I use this code: x = 'ABBA' x = ''.join(set(x)) print(x)

It results in: BA but I want it to be the first letters instead of the second letters: AB

Is there any way that I can do it without using reverse function?

CodePudding user response：

Sets in Python are still unordered unfortunately. However, dictionaries in newer versions of Python already preserve insertion order.

You can take advantage of this, by defining a dictionary with empty values, such that you can extract the keys in insertion order:

x = 'ABBA'
x = "".join({k:None for k in x}.keys())
print(x)
# AB

The idea is a bit hacky, but it works for now. Maybe in the future sets will also respect insertion order.

CodePudding user response：

Sets are unordered. so try this.


from collections import Counter


x = 'ABBA'

x = "".join(Counter(x).keys())

print(x) # AB