将数据转换为熊猫DataFrame并删除一些

Question

我有一组测量数据来转换成浮点值的数据。但有时机器不测量和设置一个“--”字符给pandas.to_numeric ValueError。这里有一个简化的例子，我的问题是如何转换成浮动孔列，并删除我有字符串“--”字符集的位置：

data = {'row_1': ["3.0", "2.4", "---", "0.0"], 'row_2': ['a', 'b', 'c', 'd']}
df = pandas.DataFrame.from_dict(data)

如何删除整个第三行并将row_1值转换为浮动？谢谢。

Answer 1

# Convert to floating point, but first make sure triple dashes can be interpreted as NaNs
df['row_1'] = df['row_1'].replace('---', 'NaN').astype(float)

# drop rows with NaNs
df = df.dropna()  

Answer 2

试试像这样的东西

import pandas as pd
data = {'row_1': ["3.0", "2.4", "---", "0.0"], 'row_2': ['a', 'b', 'c', 'd']}
df = pd.DataFrame.from_dict(data)

df = df[df['row_1']!='---'].copy()
df['row_1'] = df['row_1'].astype(float)