python - 比较Python中的浮点值

Question

当我将数据帧列(本质上是浮点型)与浮点值进行比较时，我得到了不想要的结果。我的数据框如下所示:

df
    Measurement      Year   checking
0   4.478861e-04    2015    less
1   4.478861e-04    2015    less
2   4.478861e-04    2015    less
3   4.478861e-04    2015    less
4   4.478861e-04    2015    less
5   4.478861e-04    2015    less
6   4.478861e-04    2015    less
7   4.478861e-04    2015    less
8   6.337777        2015    greater
9   8.903316        2015    greater
10  9.317186        2015    greater

数据帧的数据类型是

Measurement    float64
Year             int64
checking        object
dtype: object

当我使用以下代码过滤数据框时:

df[df['Measurement']> 5.69]

它返回空数据帧。同样，当我使用以下代码尝试使用循环进行比较时:

for i in range(len(df)):
   if df.iloc[i,'Measurement'] > 5.69:
      print('Comparison is true')

当值大于5.69时，不打印语句。谁能指导为什么代码行为异常？

Answer 1

df[df['Measurement']> 5.69] 似乎对我的数据框有用，我已经添加了代码片段。并添加了带有 if 条件的 for 循环。

import pandas as pd

data = {
    'Measurement': [4.478861e-04, 4.478861e-04, 4.478861e-04, 6.337777, 8.903316],
    'Year': [2015, 2015, 2015, 2015, 2015],
    'checking': ['less', 'less', 'less', 'greater', 'greater']
}

df = pd.DataFrame(data)
print("DataFrame:")
print(df)

result = df.dtypes

print("\nDatatypes:")
print(result)

print("\nMeasurement:")
print(df[df['Measurement']> 5.69])

measurement = df['Measurement']

print("\nMeasurements greater than 5.69:")
for x in measurement:
    if x > 5.69:
        print(x)

输出:

DataFrame:
   Measurement  Year checking
0     0.000448  2015     less
1     0.000448  2015     less
2     0.000448  2015     less
3     6.337777  2015  greater
4     8.903316  2015  greater

Datatypes:
Measurement    float64
Year             int64
checking        object
dtype: object

Measurement:
   Measurement  Year checking
3     6.337777  2015  greater
4     8.903316  2015  greater

Measurements greater than 5.69:
6.337777
8.903316