python - 如何将CSV中的多行合并为一行

Question

我收到了一个大型 CSV 文件，我需要对其进行拆分以用于机器学习。我设法找到了一种将文件拆分为我需要的 2 行的方法 - 但我遇到了问题。

我基本上有这样一个文件结构。

 "David", "Red"
 "David", "Ford"
 "David", "Blue"
 "David", "Aspergers"
 "Steve", "Red"
 "Steve", "Vauxhall"

我要求数据看起来更像这样......

"David, "Red", "Ford", "Blue", "Aspergers"
"Steve", "Red", "Vaxhaull"

我目前有这个来剥离 CSV 文件

import csv

cr = csv.reader(open("traits.csv","rb"), delimiter=',', lineterminator='\n')
cr.next() #skipping header line, no point in removing it as I need to standardise data manipuation.


# Print out the id of species and trait values
print 'Stripping input'
vals = [(row[1], row[4]) for row in cr]
print str(vals) + '\n'

with open("output.csv", "wb") as f:
    writer = csv.writer(f)
    writer.writerows(vals)
    print 'Sucessfully written to file output.csv'


#for row in cr:
#print row

Answer 1

使用字典将名称存储为键，并将列表中的其他属性存储为值:

my_dict={}
with open("traits.csv","rb") as f:
   cr = csv.reader(f, delimiter=',', lineterminator='\n')
   for row in cr:
       my_dict.setdefault(row[0].strip('" '),[]).append(row[1].strip('" '))

结果:

print my_dict
{'Steve': ['Red', 'Vauxhall'], 'David': ['Red', 'Ford', 'Blue', 'Aspergers']}

并写入新文件:

with open("output.csv", "wb") as f:
    writer = csv.writer(f,delimiter=',')
    for i,j in my_dict.iteritems():
        writer.writerow([i]+j)

setdefault(key[, default])

If key is in the dictionary, return its value. If not, insert key with a value of default and return default. default defaults to None.