python的小问题求zhu一下大家

可以问一下为什么会报ValueError: could not convert string to float: 'low'这个错吗

```python
import graphviz
import itertools
import random
from sklearn.tree import DecisionTreeClassifier, export_graphviz
from sklearn.preprocessing import OneHotEncoder
# The possible values for each class
classes = {
'supplies': ['low', 'med', 'high'],
'weather': ['raining', 'cloudy', 'sunny'],
'worked?': ['yes', 'no']
}
# Our example data from the documentation
data = [
['low', 'sunny', 'yes'],
['high', 'sunny', 'yes'],
['med', 'cloudy', 'yes'],
['low', 'raining', 'yes'],
['low', 'cloudy', 'no' ],
['high', 'sunny', 'no' ],
['high', 'raining', 'no' ],
['med', 'cloudy', 'yes'],
['low', 'raining', 'yes'],
['low', 'raining', 'no' ],
['med', 'sunny', 'no' ],
['high', 'sunny', 'yes']
]

# Our target variable, whether someone went shopping
target = ['yes', 'no', 'no', 'no', 'yes', 'no', 'no', 'no', 'no', 'yes', 'yes', 'no']
categories = [classes['supplies'], classes['weather'], classes['worked?']]
encoder = OneHotEncoder(categories)
x_data = encoder.fit_transform(data)
# Form and fit our decision tree to the now-encoded data
classifier = DecisionTreeClassifier()
tree = classifier.fit(x_data, target)
# Use our tree to predict the outcome of the random values
prediction_results = tree.predict(encoder.transform(prediction_data))


![img](https://img-mid.csdnimg.cn/release/static/image/mid/ask/880496892566126.png "#left")

哪一行报错了，你应该是把非小数的字符串转化为小数报错了