Numpy - ValueError：無法設置序列的數組元素

Question

因此，我編寫了一個小測試代碼來計算文件夾中所有csv文件的平均值。

parser = argparse.ArgumentParser(description='avg data from csv to csv') 
parser.add_argument('--input', required = True) 
parser.add_argument('--output', required = True) 
args = parser.parse_args() 

# Get command arguments 
input_files_path = args.input 
output = args.output 

avg = [] 
for infile in glob.glob(input_files_path+"*.csv"): 
     a = np.loadtxt(infile, delimiter=",") 
     mean = np.mean(a, axis=0) 
     avg.append((mean)) 
     print infile 
np.savetxt(output,(avg), fmt = "%.1f", delimiter=", ") 

但現在的問題，當我試圖保存文件的名稱，以及在CSV文件是這樣的：

parser = argparse.ArgumentParser(description='avg data from csv to csv') 
parser.add_argument('--input', required = True) 
parser.add_argument('--output', required = True) 
args = parser.parse_args() 

# Get command arguments 
input_files_path = args.input 
output = args.output 

avg = [] 
for infile in glob.glob(input_files_path+"*.csv"): 
     a = np.loadtxt(infile, delimiter=",") 
     mean = np.mean(a, axis=0) 
     avg.append((infile,(mean))) 
     print infile 
np.savetxt(output,(avg), fmt = "%.1f", delimiter=", ") 

它拋出一個錯誤：

np.savetxt(output,(avg), fmt = "%.1f", delimiter=", ") 
    File "/usr/lib/python2.7/dist-packages/numpy/lib/npyio.py", line 963, in savetxt 
    X = np.asarray(X) 
    File "/usr/lib/python2.7/dist-packages/numpy/core/numeric.py", line 235, in asarray 
    return array(a, dtype, copy=False, order=order) 
ValueError: cannot set an array element with a sequence 

我似乎不明白問題是什麼。也許這是因爲我試圖將一個字符串附加到一個浮點數？我檢查fmt在numpy ..但我沒有發現任何有趣的事情。

/usr/lib/python2.7/dist-packages/numpy/lib/npyio.py:773: UserWarning: loadtxt: Empty input file: "../robalo-31.1/op.csv" 
    warnings.warn('loadtxt: Empty input file: "%s"' % fname) 
/usr/lib/python2.7/dist-packages/numpy/core/fromnumeric.py:2374: RuntimeWarning: invalid value encountered in double_scalars 
    return mean(axis, dtype, out) 

Answer 1

我猜你的格式字符有問題np.savetxt。 （你有一個字符串浮動元組，而你的分隔符意味着你只使用浮動元素）。我建議csv此相反：

>>> import csv 
>>> import StringIO 
>>> g = StringIO.StringIO() 
>>> writer = csv.writer(g,delimiter=',') #this is the part that is applicable 
>>> writer.writerows(lst) 
>>> g.seek(0) 
>>> print g.read() 
foo,2 
bar,4 

所以我猜你的代碼可能是簡單的：

with open(output,'wb') as fout: 
    writer = csv.writer(fout,delimiter=',') 
    writer.writerows(avg) 

，而不是

np.savetxt(output,(avg), fmt = "%.1f", delimiter=", ")