按浮点数的第一个元素对元组列表进行排序：TypeError：'float'对象不可下标

Question

I am trying to sort a list of tuples of the format

[(0.001,"hello"), (0.005,"world"),(0.004,"sort"), (0.002,"me")]

This should give the output:

[(0.001, "hello"), (0.002,"me"), (0.004, "sort"), (0.005, "world")]

Currently I am using the method

sorted(my_list , key=lambda x: x[0])

This however gives the error:

TypeError: 'float' object is not subscriptable

What is the reason for this, and how can I fix it?

I am using Python version 3.6.1

Many thanks

Answer 1

You can just do my_list = sorted(my_list) to take advantage of the natural sorting mechanics of sorted() .

Also, I don't get the error you do, and I'm guessing it's because you use the reserved word list in your call to sorted(list, key=... )`. Try naming it something else.

Here's an iPython repl session:

Jupyter console 5.1.0

Python 3.6.0 (default, Dec 24 2016, 08:01:42)
Type "copyright", "credits" or "license" for more information.

IPython 5.2.2 -- An enhanced Interactive Python.
?         -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object?   -> Details about 'object', use 'object??' for extra details.



In [1]: x = [(0.001,"hello"), (0.005,"world"),(0.004,"sort"), (0.002,"me")]

In [2]: sorted(x)
Out[2]: [(0.001, 'hello'), (0.002, 'me'), (0.004, 'sort'), (0.005, 'world')]

In [3]: sorted(x, key=lambda x: x[0])
Out[3]: [(0.001, 'hello'), (0.002, 'me'), (0.004, 'sort'), (0.005, 'world')]