将一列 csv 提取到逗号分隔列表 python

Question

我有一个 CSV 文件，如下所示：

with open ("ann.csv", "rb") as annotate:
    for col in annotate:
        ann = col.lower().split(",")
        print ann[0]

我的 CSV 文件如下所示：

H1,H2,H3
da,ta,one
dat,a,two

我的输出如下所示：

da
dat

但我想要一个逗号分隔的输出，例如 (da,dat)。我怎样才能做到这一点？如果您在投票前给我一个想法，我将不胜感激。

Answer 1

不是当场打印，而是构建一个字符串，最后打印。

s = ''
with open ("ann.csv", "rb") as annotate:
    for col in annotate:
        ann = col.lower().split(",")
        s += ann[0] + ','
s = s[:-1] # Remove last comma
print(s)

我还建议更改变量名称 col，它是在行上循环，而不是在列上循环。

Answer 2

然后试试这个：

result = ''
with open ("ann.csv", "rb") as annotate:
    for col in annotate:
        ann = col.lower().split(",")
        # add first element of every line to one string and separate them by comma
        result = result + ann[0] + ','

print result

Answer 3

首先，在 Python 中您有 csv module - 使用它。

其次，您要遍历行，因此使用 col 作为变量名称有点令人困惑。

第三，只需收集列表中的项目并使用 .join():

打印

import csv
with open ("ann.csv", "rb") as csvfile:
    reader = csv.reader(csvfile)
    reader.next() # Skip the header row
    collected = []
    for row in reader:
        collected.append(row[0])
    print ",".join(collected)

Answer 4

试试这个

>>> with open ("ann.csv", "rb") as annotate:
...     for col in annotate:
...         ann = col.lower().split(",")
...         print ann[0]+',',
...

Answer 5

这样试试：

with open ("ann.csv", "rb") as annotate:
    output = []
    next(annotate)    # next will advanced the file pointer to next line
    for col in annotate:
        output.append(col.lower().split(",")[0])
    print ",".join(output)

Answer 6

使用 numpy.loadtxt 可能更容易一些：

In [23]: import numpy as np
    ...: fn = 'a.csv'
    ...: m = np.loadtxt(fn, dtype=str, delimiter=',')
    ...: print m
[['H1' 'H2' 'H3']
 ['da' 'ta' 'one']
 ['dat' 'a' 'two']]

In [24]: m[:,0][1:]
Out[24]: 
array(['da', 'dat'], 
      dtype='|S3')

In [25]: print ','.join(m[:,0][1:])
da,dat

m[:,0]获取矩阵m的第一列，[1:]跳过第一个元素'H1'.

将一列 csv 提取到逗号分隔列表 python

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