csv: writer.writerows() 分割我的字符串输入

Question

我有一个要写入 csv 文件的字符串列表。列表list_results 看起来像

['False, 60, 40 ', 'True, 70, 30, ']

所以，我会尝试这样的事情：

with open('example1.csv', 'w') as result:
    writer = csv.writer(result, delimiter=",")
    writer.writerow( ('Correct?', 'Successes', 'Failures') )
    writer.writerows(list_results)

不幸的是，数据没有写入三列。我发现：

['Correct?', 'Successes', 'Failures']  
['F', 'a', 'l', 's', 'e', ',', ' ', '6', '0', ',', ' ', '4', '0', ' ']  
['T', 'r', 'u', 'e', ',', ' ', '7', '0', ',', ' ', '3', '0', ',', ' ']

如何适当地格式化此行为以获取

['Correct?', 'Successes', 'Failures']  
['False', 60, 40]  
['True', 70, 30]

最好采用%s %d %d 格式？

Answer 1

您使用的是writer.writerows()，末尾带有s。该方法需要一个列表列表，但您传入了一个字符串列表。 writerows() 方法本质上是这样做的：

def writerows(self, rows):
    for row in rows:
        self.writerow(row)

其中每一行必须是一系列列。字符串是单个字符的序列，所以这就是您所写的：由您选择的分隔符分隔的单个字符。

你需要将你的字符串分成几列，不要自己包含逗号，包含这些是 writer 对象的工作：

with open('example1.csv', 'w') as result:
    writer = csv.writer(result, delimiter=",")
    writer.writerow(('Correct?', 'Successes', 'Failures'))
    for row in list_results:
        columns = [c.strip() for c in row.strip(', ').split(',')]
        writer.writerow(columns)

或使用生成器表达式，以便您可以继续使用writerows()：

with open('example1.csv', 'w') as result:
    writer = csv.writer(result, delimiter=",")
    writer.writerow(('Correct?', 'Successes', 'Failures'))
    writer.writerows([c.strip() for c in r.strip(', ').split(',')]
                     for r in list_results)

演示：

>>> import csv
>>> list_results = ['False, 60, 40 ', 'True, 70, 30, ']
>>> import csv
>>> import sys
>>> list_results = ['False, 60, 40 ', 'True, 70, 30, ']
>>> writer = csv.writer(sys.stdout)
>>> writer.writerow(('Correct?', 'Successes', 'Failures'))
Correct?,Successes,Failures
>>> for row in list_results:
...     columns = [c.strip() for c in row.strip(', ').split(',')]
...     writer.writerow(columns)
...
False,60,40
True,70,30
>>> writer.writerows([c.strip() for c in r.strip(', ').split(',')]
...                  for r in list_results)
False,60,40
True,70,30

Answer 2

您的list_results 很可能包含以下内容：

['False, 60, 40 ', 'True, 70, 30, ']

writerows() 接受一个列表列表，你提供一个字符串列表，一个字符串是可迭代的，因此被转换为字符列表，你想要的是：

with open('example1.csv', 'w') as result:
    writer = csv.writer(result, delimiter=",")
    writer.writerow( ('Correct?', 'Successes', 'Failures') )
    writer.writerows([c.strip() for c in r.split(',')] for r in list_results)

Answer 3

效果很好：

list_results = [(False, 60, 40), (True, 70, 30)]

这是 C 上 writer.writerows() 的源代码。

static PyObject *
csv_writerows(WriterObj *self, PyObject *seqseq)
{
    PyObject *row_iter, *row_obj, *result;

row_iter = PyObject_GetIter(seqseq);
if (row_iter == NULL) {
    PyErr_SetString(PyExc_TypeError,
                    "writerows() argument must be iterable");
    return NULL;
}
while ((row_obj = PyIter_Next(row_iter))) {
    result = csv_writerow(self, row_obj);
    Py_DECREF(row_obj);
    if (!result) {
        Py_DECREF(row_iter);
        return NULL;
    }
    else
         Py_DECREF(result);
}
Py_DECREF(row_iter);
if (PyErr_Occurred())
    return NULL;
Py_INCREF(Py_None);
return Py_None;


}

Answer 4

writerows 需要一个列表列表。所以如果你给writerows一个列表，它会将它转换为列表列表（即将单词分割成字母。

import csv
list_results = ['False, 60, 40 ', 'True, 70, 30, ']

with open(r"C:\test.csv", 'wb') as result:
    writer = csv.writer(result, delimiter=",")
    writer.writerow( ('Correct?', 'Successes', 'Failures') )
    writer.writerows([i.strip().split(',') for i in list_results])

或者如果你想使用writerow-

import csv
list_results = ['False, 60, 40 ', 'True, 70, 30, ']

with open(r"C:\mnp_.csv", 'wb') as result:
    writer = csv.writer(result, delimiter=",")
    writer.writerow( ('Correct?', 'Successes', 'Failures') )
    data = [i.strip().split(',') for i in list_results]
    for d in data:
        writer.writerow(d)

输出-

Correct?    Successes   Failures
FALSE   60  40
TRUE    70  30