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python - 比较 Python 中的浮点数

问题描述

我在比较 python 中的条件语句中的浮点数时遇到问题。我有一个如下所示的数据集：

         CVE-ID CVE Creation Date  Patch Date  CVSS Score  \
0   CVE-2012-6702          6/3/2016    6/7/2016         5.9   
1   CVE-2015-8951         8/15/2016  12/16/2015         7.8   
2   CVE-2015-9016         3/28/2017   8/15/2015         7.0   
3  CVE-2016-10230          3/1/2017  11/28/2016         9.8   
4  CVE-2016-10231          3/1/2017  12/14/2016         7.8   

                                     Bug Description  # of lines added  \
0  Expat, when used in a parser that has not call...                41   
1  Multiple use-after-free vulnerabilities in sou...                10   
2  In blk_mq_tag_to_rq in blk-mq.c in the upstrea...                 3   
3  A remote code execution vulnerability in the Q...                 7   
4  An elevation of privilege vulnerability in the...                 8   

   number of lines removed  Vuln Type  Diff of dates  
0                        7        UNK              4  
1                        3     #NAME?           -243  
2                        1        UNK           -591  
3                        0  Exec Code            -93  
4                        0        UNK            -77

我想要完成的是循环遍历 CVSS 分数（类型 float），如果它在 0<=score<6 范围内，那么我在该行（类号）中添加一列并使其等于 1。如果它在 6<=score<7.5 范围内，则班级编号为 2，如果在 7.5<=score<10 范围内，则班级编号为 3。如果正确完成，这应该是这样的：

           CVE-ID CVE Creation Date  Patch Date  CVSS Score  \
0   CVE-2012-6702          6/3/2016    6/7/2016         5.9   
1   CVE-2015-8951         8/15/2016  12/16/2015         7.8   
2   CVE-2015-9016         3/28/2017   8/15/2015         7.0   
3  CVE-2016-10230          3/1/2017  11/28/2016         9.8   
4  CVE-2016-10231          3/1/2017  12/14/2016         7.8   

                                     Bug Description  # of lines added  \
0  Expat, when used in a parser that has not call...                41   
1  Multiple use-after-free vulnerabilities in sou...                10   
2  In blk_mq_tag_to_rq in blk-mq.c in the upstrea...                 3   
3  A remote code execution vulnerability in the Q...                 7   
4  An elevation of privilege vulnerability in the...                 8   

   number of lines removed  Vuln Type  Diff of dates Class Number  
0                        7        UNK              4            1  
1                        3     #NAME?           -243            3  
2                        1        UNK           -591            2  
3                        0  Exec Code            -93            3  
4                        0        UNK            -77            3

我的代码现在看起来像这样：

data = pd.read_csv('tag_SA.txt', sep='|')
for score in data['CVSS Score']:
    if 0.0 < score < 6.0:
        data["Class Number"] = 1
    elif(6 <= score < 7.5):
        data["Class Number"] = 2
    else:
        data["Class Number"] = 3

我得到的输出是这样的：

           CVE-ID CVE Creation Date  Patch Date  CVSS Score  \
0   CVE-2012-6702          6/3/2016    6/7/2016         5.9   
1   CVE-2015-8951         8/15/2016  12/16/2015         7.8   
2   CVE-2015-9016         3/28/2017   8/15/2015         7.0   
3  CVE-2016-10230          3/1/2017  11/28/2016         9.8   
4  CVE-2016-10231          3/1/2017  12/14/2016         7.8   

                                     Bug Description  # of lines added  \
0  Expat, when used in a parser that has not call...                41   
1  Multiple use-after-free vulnerabilities in sou...                10   
2  In blk_mq_tag_to_rq in blk-mq.c in the upstrea...                 3   
3  A remote code execution vulnerability in the Q...                 7   
4  An elevation of privilege vulnerability in the...                 8   

   number of lines removed  Vuln Type  Diff of dates Class Number  
0                        7        UNK              4            3  
1                        3     #NAME?           -243            3  
2                        1        UNK           -591            3  
3                        0  Exec Code            -93            3  
4                        0        UNK            -77            3

所以它只是去 else 语句并认为其他语句是错误的。python中的浮点比较有什么我缺少的吗？任何帮助，将不胜感激

标签： pythonpandas

解决方案

您的问题不在于比较浮点数，而是您在分配时覆盖了数据框的整个列。

您只需要设置满足条件的那些行，请参阅 https://pandas.pydata.org/pandas-docs/stable/user_guide/indexing.html，您可能还应该查看https://pandas.pydata .org/pandas-docs/stable/user_guide/10min.html。

使用那里记录的内容：

data = pd.read_csv('tag_SA.txt', sep='|')


data['Class Number'] = 3

mask = (0.0 < data['CVSS Score']) & (data['CVSS Score'] <= 6.0)
data.loc[mask, 'Class Number'] = 1

mask = (6.0 < data['CVSS Score']) & (data['CVSS Score'] <= 7.5)
data.loc[mask, 'Class Number'] = 2

你也可以pandas.cut这样使用：

max_val = data['CVSS Score'].max()
# codes start at 0, add 1 if needed
data['Class Number'] = pd.cut(data['CVSS Score'], [0, 6, 7.5, max_val]).codes + 1

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