Python：URL数据到csv阅读器

Question

我试图在Python中将url请求的结果转换为CSV reader object。输出看起来不错，但出现以下错误：

for study_id, sample_id, run_id in reader: 
ValueError: not enough values to unpack (expected 3, got 1) 

首先，我请求数据，并将其转换为字符串数据：

req = urllib.request.Request(url=url_get_project_runs, headers={'Content-Type': 'text/plain'}) 
     res = urllib.request.urlopen(req) 
     dec_res = res.read().decode() 
     sys.stderr.write(str(dec_res)) --> for the print see below 
     return dec_res 

打印会给这样的：

ERP001736,ERS494374,ERR598958 
ERP001736,ERS494394,ERR598963 
ERP001736,ERS494431,ERR598964 
ERP001736,ERS494445,ERR599170 
ERP001736,ERS494488,ERR598996 
ERP001736,ERS494518,ERR598976 
ERP001736,ERS494559,ERR598986 
ERP001736,ERS494579,ERR599078 
ERP001736,ERS494616,ERR598944 
ERP001736,ERS494628,ERR599001 
ERP001736,ERS488919,ERR1701760 

这对我来说似乎很好，因为这些项目用逗号分开，“行”完好无损。 但是，如果我用这个作为一个CSV阅读器的输入，并尝试打印三列，如下：会发生

reader = csv.reader(dec_res, delimiter=',') 
     for study_id, sample_id, run_id in reader: 
      print(study_id + ", " + sample_id + ", " + run_id) 

以下错误： ValueError: not enough values to unpack (expected 3, got 1)

我还测试了一些代码发现问题：

for row in reader: 
      sys.stderr.write(str(row)) 

这将给：

['E']['R']['P']['0']['0']['1']['7']['3']['6']['', '']['E']['R']['S']['4']['7']...etc 

Answer 1

您正在将str传递给csv阅读器，它需要一行一行地迭代。 str是逐个字符可迭代的。用StringIO或使用splitlines（或任何其他方法提供逐行迭代）来包装您的字符串。

import csv 
from io import StringIO 

dec_res = """ERP001736,ERS494374,ERR598958 
ERP001736,ERS494394,ERR598963 
ERP001736,ERS494431,ERR598964 
ERP001736,ERS494445,ERR599170 
ERP001736,ERS494488,ERR598996 
ERP001736,ERS494518,ERR598976 
ERP001736,ERS494559,ERR598986 
ERP001736,ERS494579,ERR599078 
ERP001736,ERS494616,ERR598944 
ERP001736,ERS494628,ERR599001 
ERP001736,ERS488919,ERR1701760""" 

reader = csv.reader(StringIO(dec_res), delimiter=',') 
#reader = csv.reader(dec_res.splitlines(), delimiter=',') 

for study_id, sample_id, run_id in reader: 
    print(study_id + ", " + sample_id + ", " + run_id)