Numpy savetxt Structured Array ValueError: fmt has wrong number of % formats

Question

import numpy as np

row_a = ['0.01722497', '', '0.09496404', '0.03654174', '0.03624997', '0.01583785', '0.02002064', '0.13934049', '0.0405615', '0.05686177', '', '0.08495372', '0.00619173', '0.00515492', '0.01053369', '0.06576333']
row_b = [0.04871661, 0.1122536, 0.20836956, 0.05473605, 0.02344445, 0.01739371, 0.00524003, 0.0640286, 0.02766152, 0.02442267, 0.04183814, 0.04853815, 0.01682549, 0.00263045, 0.00819199, 0.1631007]
dt = np.dtype([('col_1', 'U32'), ('col_2', float)])
arr = np.empty((2, len(row_a)), dtype=dt)
arr['col_1'] = row_a
arr['col_2'] = row_b
np.savetxt('table.csv', arr, delimiter=',', header='col_1,col_2', fmt='%s %f')

上面的代码（应该从 str 和 int 数组创建结构化数组并将其输出到 csv）给出了以下错误，即使我有 2 个相同长度的数组，2 列和 2格式：

ValueError: fmt has wrong number of % formats:  %s %f

Answer 1

制作一维结构化数组（根据我的评论）：

In [423]: row_a = ['0.01722497', '', '0.09496404', '0.03654174', '0.03624997', '0.01583785', '0
     ...: .02002064', '0.13934049', '0.0405615', '0.05686177', '', '0.08495372', '0.00619173',
     ...: '0.00515492', '0.01053369', '0.06576333']
     ...: row_b = [0.04871661, 0.1122536, 0.20836956, 0.05473605, 0.02344445, 0.01739371, 0.005
     ...: 24003, 0.0640286, 0.02766152, 0.02442267, 0.04183814, 0.04853815, 0.01682549, 0.00263
     ...: 045, 0.00819199, 0.1631007]
     ...: dt = np.dtype([('col_1', 'U32'), ('col_2', float)])
     ...: arr = np.empty(len(row_a), dtype=dt)
     ...: arr['col_1'] = row_a
     ...: arr['col_2'] = row_b
In [424]: 
In [424]: arr
Out[424]: 
array([('0.01722497', 0.04871661), ('', 0.1122536 ),
       ('0.09496404', 0.20836956), ('0.03654174', 0.05473605),
       ('0.03624997', 0.02344445), ('0.01583785', 0.01739371),
       ('0.02002064', 0.00524003), ('0.13934049', 0.0640286 ),
       ('0.0405615', 0.02766152), ('0.05686177', 0.02442267),
       ('', 0.04183814), ('0.08495372', 0.04853815),
       ('0.00619173', 0.01682549), ('0.00515492', 0.00263045),
       ('0.01053369', 0.00819199), ('0.06576333', 0.1631007 )],
      dtype=[('col_1', '<U32'), ('col_2', '<f8')])
In [425]: arr.shape
Out[425]: (16,)

保存：

In [426]: np.savetxt('table.csv', arr, delimiter=',', header='col_1,col_2', fmt='%s %f')
In [427]: cat table.csv
# col_1,col_2
0.01722497 0.048717
 0.112254
0.09496404 0.208370
0.03654174 0.054736
...

我之前回答的链接 SO 有一个更复杂的数据类型。这是一个简单的 2 字段案例，因此不需要特殊处理。

""" 值可能会在文件加载时出现问题。我建议至少使用像 , 这样的定界符，这样加载程序就可以将其视为缺失值。

In [428]: np.savetxt('table.csv', arr, delimiter=',', header='col_1,col_2', fmt='%s, %f')
In [429]: cat table.csv
# col_1,col_2
0.01722497, 0.048717
, 0.112254
0.09496404, 0.208370
0.03654174, 0.054736
...
In [430]: np.genfromtxt('table.csv', dtype=None, names=True, delimiter=',')
Out[430]: 
array([(0.01722497, 0.048717), (       nan, 0.112254),
       (0.09496404, 0.20837 ), (0.03654174, 0.054736),
       (0.03624997, 0.023444), (0.01583785, 0.017394),

In [431]: np.genfromtxt('table.csv', dtype=arr.dtype, names=True, delimiter=',')
Out[431]: 
array([('0.01722497', 0.048717), ('', 0.112254), ('0.09496404', 0.20837 ),
       ('0.03654174', 0.054736), ('0.03624997', 0.023444),
       ('0.01583785', 0.017394), ('0.02002064', 0.00524 ),

Numpy savetxt Structured Array ValueError: fmt has wrong number of % formats

Numpy savetxt Structured Array ValueError: fmt has wrong number of % formats

csv

numpy

structured-array