如何使用python计算csv文件中具有条件的元素

Question

我不熟悉python语言。我有一个csv格式的表，有n列，其中标题是Tax_id，每列包含如下物种名称

9606                  9606.1               508771  
0                root                root                  root    
1  cellular organisms  cellular organisms    cellular organisms
2           Eukaryota           Eukaryota             Eukaryota
3        Opisthokonta        Opisthokonta                   Sar
4             Metazoa             Metazoa             Alveolata
5           Eumetazoa           Eumetazoa           Apicomplexa
6           Bilateria           Bilateria           Conoidasida
7       Deuterostomia       Deuterostomia              Coccidia
8            Chordata            Chordata        Eucoccidiorida
9            Craniata            Craniata           Eimeriorina

我想做的是能够编写一个python代码，只为包含名为“后生动物”的物种的列计算每个物种的出现次数

#to return something like

    Eumetazoa 2
    Bilateria 2
    Craniata  2

Answer 1

我还不能完全确定你想要什么。这样行吗？注意：您需要为此（How to install pandas）安装程序包pandas

我假设您的CSV文件如下所示：

s = '''9606,9606.1,508771
0,root,root,root
1,cellular organisms,cellular organisms,cellular organisms
2,Eukaryota,Eukaryota,Eukaryota
3,Opisthokonta,Opisthokonta,Sar
4,Metazoa,Metazoa,Alveolata
5,Eumetazoa,Eumetazoa,Apicomplexa
6,Bilateria,Bilateria,Conoidasida
7,Deuterostomia,Deuterostomia,Coccidia
8,Chordata,Chordata,Eucoccidiorida
9,Craniata,Craniata,Eimeriorina'''

算法：

import pandas as pd
from io import StringIO

def filter_and_count(df, search_string):
    df_filtered = df.loc[:, (df == search_string).any(axis=0)]
    return pd.melt(df_filtered)['value'].value_counts()

df = pd.read_csv(StringIO(s))  # replace this with read_csv("filename")
print(filter_and_count(df, 'Metazoa'))

输出：

root                  2
Metazoa               2
Deuterostomia         2
Craniata              2
cellular organisms    2
Chordata              2
Eumetazoa             2
Opisthokonta          2
Eukaryota             2
Bilateria             2
Name: value, dtype: int64