如何在Python中的每个字符串内基于浮点数对列表进行排序？

Question

I am trying to figure out how to sort a list based on a certain part of each string. How do I write the key?

myKey(e)
  return e[-5,-2]

print(sorted(["A: (" + str(round(7.24856, 2)) + ")", "B: (" + str(round(5.8333, 2)) + ")"], key = myKey))

I want the output to look like this: ['B: (5.83)', 'A: (7.25)']

In my full code, there are more than two strings in the list, so I cannot just sort them reversed alphabetically.

Thank you

Answer 1

Your syntax for function myKey is wrong. Other than that, you have to slice out the number in the string with the correct index (from index of char '(' + 1 to the character before the last) and convert them to floating point number value so that the sorted function can work properly.

def myKey(e):
  return float(e[e.index('(')+1:-1])
print(sorted(["A: (" + str(round(7.24856, 2)) + ")", "B: (" + str(round(5.8333, 2)) + ")"], key = myKey))

Answer 2

You can use tuples sorted() to sort your data alongside with some list and string expressions to get the desired output:

input_list = ['A:(100.27)', 'B:(2.36)', 'C:(75.96)', 'D:(55.78)']
tuples_list = [(e.split(':(')[0], float(e.split(':(')[1][:-1])) for e in input_list]
sorted_tuples = sorted(tuples_list, key=lambda x: x[1])
result = [x[0] +':('+ str(x[1]) +')' for x in sorted_tuples]

print(input_list)
print(tuples_list)
print(sorted_tuples)
print(result)

Output:

['A:(100.27)', 'B:(2.36)', 'C:(75.96)', 'D:(55.78)']
[('A', 100.27), ('B', 2.36), ('C', 75.96), ('D', 55.78)]
[('B', 2.36), ('D', 55.78), ('C', 75.96), ('A', 100.27)]
['B:(2.36)', 'D:(55.78)', 'C:(75.96)', 'A:(100.27)']