将字符串列表转换为float [英] Turning a list of strings into float

问题描述

我从外部文件中打印了一些数据，并将数据拆分为一个字符串:

I printed some data from an external file and split the data into a string:

string = data
splitstring = string.split(',')
print(splitstring)

这给了我

['500', '500', '0.5', '50', '1.0', '0.75', '0.50', '0.25', '0.00']

我试图使用这种方法将它们变成浮点数:

I tried to turn them into floats using this method:

for c in splitstring:
    splitstring[c]=float(splitstring[c])

但是它给了我这个错误:

But it gives me this error:

Traceback (most recent call last):
  File "/Users/katiemoore/Documents/MooreKatie_assign10_attempt2.py", line 44, in <module>
    splitstring[c]=float(splitstring[c])
 TypeError: list indices must be integers, not str

推荐答案

使用列表理解:

splitstring = [float(s) for s in splitstring]

，或者在Python 2上，为了提高速度，请使用map():

or, on Python 2, for speed, use map():

splitstring = map(float, splitstring)

当您在Python中循环访问列表时，没有得到索引，而是得到了值，因此c不是整数，而是字符串值(第一次迭代.)

When you loop over a list in Python, you don't get indexes, you get the values themselves, so c is not an integer but a string value ('500' in the first iteration).

您必须使用enumerate()为您生成索引以及实际值:

You'd have to use enumerate() to generate indices for you, together with the actual values:

for i, value in enumerate(splitstring):
    splitstring[i] = float(value)

或使用for c in range(len(splitstring)):仅 生成索引.但是无论如何，列表理解和map()选项还是更好.

or use for c in range(len(splitstring)): to only produce indices. But the list comprehension and map() options are better anyway.

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