import numpy as np
A = np.array([(1,'First',0.5,1+2j),(2,'Second',1.5,1+3j),(3,'Third',0.8,1-2j)],dtype=('i2,a6,f4,c8'))
A
Out[3]:
array([(1, b'First', 0.5 , 1.+2.j),
(2, b'Second', 1.5 , 1.+3.j),
(3, b'Third', 0.80000001, 1.-2.j)],
dtype=[('f0', '<i2'), ('f1', 'S6'), ('f2', '<f4'), ('f3', '<c8')])
A[1]
Out[4]: (2, b'Second', 1.5, 1.+3.j)
A['f2']
Out[5]: array([ 0.5 , 1.5 , 0.80000001], dtype=float32)
A['f1']
Out[6]:
array([b'First', b'Second', b'Third'],
dtype='|S6')
A = np.array([(1,'First',0.5,1+2j),(2,'Second',1.5,1+3j),(3,'Third',0.8,1-2j)],dtype=[('id','i2'),('position','a6'),('value','f4'),('complex','c8')])
A
Out[8]:
array([(1, b'First', 0.5 , 1.+2.j),
(2, b'Second', 1.5 , 1.+3.j),
(3, b'Third', 0.80000001, 1.-2.j)],
dtype=[('id', '<i2'), ('position', 'S6'), ('value', '<f4'), ('complex', '<c8')])
A = np.array([(1,'First',0.5,1+2j),(2,'Second',1.5,1+3j),(3,'Third',0.8,1-2j)])
A
Out[10]:
array([['1', 'First', '0.5', '(1+2j)'],
['2', 'Second', '1.5', '(1+3j)'],
['3', 'Third', '0.8', '(1-2j)']],
dtype='<U11')
A.dtype.names = ('id','position','value','complex')
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
<ipython-input-11-4f156499990d> in <module>()
----> 1 A.dtype.names = ('id','position','value','complex')
ValueError: there are no fields defined
A = np.array([(1,'First',0.5,1+2j),(2,'Second',1.5,1+3j),(3,'Third',0.8,1-2j)],dtype=[('id','i2'),('position','a6'),('value','f4'),('complex','c8')])
A
Out[13]:
array([(1, b'First', 0.5 , 1.+2.j),
(2, b'Second', 1.5 , 1.+3.j),
(3, b'Third', 0.80000001, 1.-2.j)],
dtype=[('id', '<i2'), ('position', 'S6'), ('value', '<f4'), ('complex', '<c8')])
A.dtype.names = ('id','order','value','complex')
A['order']
Out[15]:
array([b'First', b'Second', b'Third'],
dtype='|S6')
data = np.arange(1,17).reshape(4,4)
data
Out[17]:
array([[ 1, 2, 3, 4],
[ 5, 6, 7, 8],
[ 9, 10, 11, 12],
[13, 14, 15, 16]])
np.save('saved_data',data)
loaded_data = np.load('saved_data.npy')
loaded_data
Out[20]:
array([[ 1, 2, 3, 4],
[ 5, 6, 7, 8],
[ 9, 10, 11, 12],
[13, 14, 15, 16]])
data = np.genfromtxt('E:\0.0\pythondemo\demo1\tdemo.csv',delimiter=',',names=True)
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
<ipython-input-21-dacc8747616f> in <module>()
----> 1 data = np.genfromtxt('E:\0.0\pythondemo\demo1\tdemo.csv',delimiter=',',names=True)
D:\ProgramData\Anaconda3\lib\site-packages\numpy\lib\npyio.py in genfromtxt(fname, dtype, comments, delimiter, skip_header, skip_footer, converters, missing_values, filling_values, usecols, names, excludelist, deletechars, replace_space, autostrip, case_sensitive, defaultfmt, unpack, usemask, loose, invalid_raise, max_rows)
1549 fhd = iter(np.lib._datasource.open(fname, 'rbU'))
1550 else:
-> 1551 fhd = iter(np.lib._datasource.open(fname, 'rb'))
1552 own_fhd = True
1553 else:
D:\ProgramData\Anaconda3\lib\site-packages\numpy\lib\_datasource.py in open(path, mode, destpath)
149
150 ds = DataSource(destpath)
--> 151 return ds.open(path, mode)
152
153
D:\ProgramData\Anaconda3\lib\site-packages\numpy\lib\_datasource.py in open(self, path, mode)
492
493 # NOTE: _findfile will fail on a new file opened for writing.
--> 494 found = self._findfile(path)
495 if found:
496 _fname, ext = self._splitzipext(found)
D:\ProgramData\Anaconda3\lib\site-packages\numpy\lib\_datasource.py in _findfile(self, path)
335
336 for name in filelist:
--> 337 if self.exists(name):
338 if self._isurl(name):
339 name = self._cache(name)
D:\ProgramData\Anaconda3\lib\site-packages\numpy\lib\_datasource.py in exists(self, path)
440
441 # Test local path
--> 442 if os.path.exists(path):
443 return True
444
D:\ProgramData\Anaconda3\lib\genericpath.py in exists(path)
17 """Test whether a path exists. Returns False for broken symbolic links"""
18 try:
---> 19 os.stat(path)
20 except OSError:
21 return False
ValueError: stat: embedded null character in path
data = np.genfromtxt(r'E:\0.0\pythondemo\demo1\tdemo.csv',delimiter=',',names=True)
---------------------------------------------------------------------------
UnicodeDecodeError Traceback (most recent call last)
<ipython-input-22-bbff58f6826a> in <module>()
----> 1 data = np.genfromtxt(r'E:\0.0\pythondemo\demo1\tdemo.csv',delimiter=',',names=True)
D:\ProgramData\Anaconda3\lib\site-packages\numpy\lib\npyio.py in genfromtxt(fname, dtype, comments, delimiter, skip_header, skip_footer, converters, missing_values, filling_values, usecols, names, excludelist, deletechars, replace_space, autostrip, case_sensitive, defaultfmt, unpack, usemask, loose, invalid_raise, max_rows)
1605 if names is True:
1606 names = validate_names([_bytes_to_name(_.strip())
-> 1607 for _ in first_values])
1608 first_line = b''
1609 elif _is_string_like(names):
D:\ProgramData\Anaconda3\lib\site-packages\numpy\lib\npyio.py in <listcomp>(.0)
1605 if names is True:
1606 names = validate_names([_bytes_to_name(_.strip())
-> 1607 for _ in first_values])
1608 first_line = b''
1609 elif _is_string_like(names):
D:\ProgramData\Anaconda3\lib\site-packages\numpy\lib\_iotools.py in _bytes_to_name(s)
23
24 def _bytes_to_name(s):
---> 25 return s.decode('ascii')
26 else:
27 _bytes_to_complex = complex
UnicodeDecodeError: 'ascii' codec can't decode byte 0xd0 in position 0: ordinal not in range(128)
data = np.genfromtxt(r'E:\0.0\pythondemo\demo1\tdemo.csv',delimiter=',',names=True)
data
Out[24]:
array([( 1., 123., 1.4, 23.), ( 2., 110., 0.5, 18.),
( 3., 164., 2.1, 19.)],
dtype=[('id', '<f8'), ('value1', '<f8'), ('value2', '<f8'), ('value3', '<f8')])
# 内容为空的项填充为nan值
data['id']
Out[26]: array([ 1., 2., 3.])
data[1]
Out[27]: ( 2., 110., 0.5, 18.)
