description emptyempty_like create new arrays by allocating new memorybut do not populate with any values like ones and zeros eyeidentity create square identity matrix ( ' on the diagonal and ' elsewheredata types for ndarrays the data type or dtype is special object containing the information the ndarray needs to interpret chunk of memory as particular type of datain [ ]arr np array([ ]dtype=np float in [ ]arr np array([ ]dtype=np int in [ ]arr dtype out[ ]dtype('float 'in [ ]arr dtype out[ ]dtype('int 'dtypes are part of what make numpy so powerful and flexible in most cases they map directly onto an underlying machine representationwhich makes it easy to read and write binary streams of data to disk and also to connect to code written in low-level language like or fortran the numerical dtypes are named the same waya type namelike float or intfollowed by number indicating the number of bits per element standard double-precision floating point value (what' used under the hood in python' float objecttakes up bytes or bits thusthis type is known in numpy as float see table - for full listing of numpy' supported data types don' worry about memorizing the numpy dtypesespecially if you're new user it' often only necessary to care about the general kind of data you're dealing withwhether floating pointcomplexintegerbooleanstringor general python object when you need more control over how data are stored in memory and on diskespecially large data setsit is good to know that you have control over the storage type table - numpy data types type type code description int uint signed and unsigned -bit ( byteinteger types int uint signed and unsigned -bit integer types int uint signed and unsigned -bit integer types int uint signed and unsigned -bit integer types float half-precision floating point float or standard single-precision floating point compatible with float float float or standard double-precision floating point compatible with double and python float object the numpy ndarraya multidimensional array object www it-ebooks info