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.)
