numpy.core.defchararray.chararray¶
-
class
numpy.core.defchararray.
chararray
(shape, itemsize=1, unicode=False, buffer=None, offset=0, strides=None, order=None)[source]¶ Provides a convenient view on arrays of string and unicode values.
Note
The
chararray
class exists for backwards compatibility with Numarray, it is not recommended for new development. Starting from numpy 1.4, if one needs arrays of strings, it is recommended to use arrays ofdtype
object_
,string_
orunicode_
, and use the free functions in thenumpy.char
module for fast vectorized string operations.Versus a regular NumPy array of type str or unicode, this class adds the following functionality:
- values automatically have whitespace removed from the end when indexed
- comparison operators automatically remove whitespace from the end when comparing values
- vectorized string operations are provided as methods
(e.g.
endswith
) and infix operators (e.g."+", "*", "%"
)
chararrays should be created using
numpy.char.array
ornumpy.char.asarray
, rather than this constructor directly.This constructor creates the array, using buffer (with offset and
strides
) if it is notNone
. If buffer isNone
, then constructs a new array withstrides
in “C order”, unless bothlen(shape) >= 2
andorder='Fortran'
, in which casestrides
is in “Fortran order”.Parameters: shape : tuple
Shape of the array.
itemsize : int, optional
Length of each array element, in number of characters. Default is 1.
unicode : bool, optional
Are the array elements of type unicode (True) or string (False). Default is False.
buffer : int, optional
Memory address of the start of the array data. Default is None, in which case a new array is created.
offset : int, optional
Fixed stride displacement from the beginning of an axis? Default is 0. Needs to be >=0.
strides : array_like of ints, optional
Strides for the array (see
ndarray.strides
for full description). Default is None.order : {‘C’, ‘F’}, optional
The order in which the array data is stored in memory: ‘C’ -> “row major” order (the default), ‘F’ -> “column major” (Fortran) order.
Examples
>>> charar = np.chararray((3, 3)) >>> charar[:] = 'a' >>> charar chararray([['a', 'a', 'a'], ['a', 'a', 'a'], ['a', 'a', 'a']], dtype='|S1')
>>> charar = np.chararray(charar.shape, itemsize=5) >>> charar[:] = 'abc' >>> charar chararray([['abc', 'abc', 'abc'], ['abc', 'abc', 'abc'], ['abc', 'abc', 'abc']], dtype='|S5')
Attributes
T
Same as self.transpose(), except that self is returned if self.ndim < 2. base
Base object if memory is from some other object. ctypes
An object to simplify the interaction of the array with the ctypes module. data
Python buffer object pointing to the start of the array’s data. dtype
Data-type of the array’s elements. flags
Information about the memory layout of the array. flat
A 1-D iterator over the array. imag
The imaginary part of the array. itemsize
Length of one array element in bytes. nbytes
Total bytes consumed by the elements of the array. ndim
Number of array dimensions. real
The real part of the array. shape
Tuple of array dimensions. size
Number of elements in the array. strides
Tuple of bytes to step in each dimension when traversing an array. Methods
astype
(dtype[, order, casting, subok, copy])Copy of the array, cast to a specified type. argsort
([axis, kind, order])Returns the indices that would sort this array. copy
([order])Return a copy of the array. count
(sub[, start, end])Returns an array with the number of non-overlapping occurrences of substring sub in the range [start, end]. decode
([encoding, errors])Calls str.decode element-wise. dump
(file)Dump a pickle of the array to the specified file. dumps
()Returns the pickle of the array as a string. encode
([encoding, errors])Calls str.encode element-wise. endswith
(suffix[, start, end])Returns a boolean array which is True where the string element in self ends with suffix, otherwise False. expandtabs
([tabsize])Return a copy of each string element where all tab characters are replaced by one or more spaces. fill
(value)Fill the array with a scalar value. find
(sub[, start, end])For each element, return the lowest index in the string where substring sub is found. flatten
([order])Return a copy of the array collapsed into one dimension. getfield
(dtype[, offset])Returns a field of the given array as a certain type. index
(sub[, start, end])Like find
, but raises ValueError when the substring is not found.isalnum
()Returns true for each element if all characters in the string are alphanumeric and there is at least one character, false otherwise. isalpha
()Returns true for each element if all characters in the string are alphabetic and there is at least one character, false otherwise. isdecimal
()For each element in self, return True if there are only decimal characters in the element. isdigit
()Returns true for each element if all characters in the string are digits and there is at least one character, false otherwise. islower
()Returns true for each element if all cased characters in the string are lowercase and there is at least one cased character, false otherwise. isnumeric
()For each element in self, return True if there are only numeric characters in the element. isspace
()Returns true for each element if there are only whitespace characters in the string and there is at least one character, false otherwise. istitle
()Returns true for each element if the element is a titlecased string and there is at least one character, false otherwise. isupper
()Returns true for each element if all cased characters in the string are uppercase and there is at least one character, false otherwise. item
(*args)Copy an element of an array to a standard Python scalar and return it. join
(seq)Return a string which is the concatenation of the strings in the sequence seq. ljust
(width[, fillchar])Return an array with the elements of self left-justified in a string of length width. lower
()Return an array with the elements of self converted to lowercase. lstrip
([chars])For each element in self, return a copy with the leading characters removed. nonzero
()Return the indices of the elements that are non-zero. put
(indices, values[, mode])Set a.flat[n] = values[n]
for all n in indices.ravel
([order])Return a flattened array. repeat
(repeats[, axis])Repeat elements of an array. replace
(old, new[, count])For each element in self, return a copy of the string with all occurrences of substring old replaced by new. reshape
(shape[, order])Returns an array containing the same data with a new shape. resize
(new_shape[, refcheck])Change shape and size of array in-place. rfind
(sub[, start, end])For each element in self, return the highest index in the string where substring sub is found, such that sub is contained within [start, end]. rindex
(sub[, start, end])Like rfind
, but raises ValueError when the substring sub is not found.rjust
(width[, fillchar])Return an array with the elements of self right-justified in a string of length width. rsplit
([sep, maxsplit])For each element in self, return a list of the words in the string, using sep as the delimiter string. rstrip
([chars])For each element in self, return a copy with the trailing characters removed. searchsorted
(v[, side, sorter])Find indices where elements of v should be inserted in a to maintain order. setfield
(val, dtype[, offset])Put a value into a specified place in a field defined by a data-type. setflags
([write, align, uic])Set array flags WRITEABLE, ALIGNED, (WRITEBACKIFCOPY and UPDATEIFCOPY), respectively. sort
([axis, kind, order])Sort an array, in-place. split
([sep, maxsplit])For each element in self, return a list of the words in the string, using sep as the delimiter string. splitlines
([keepends])For each element in self, return a list of the lines in the element, breaking at line boundaries. squeeze
([axis])Remove single-dimensional entries from the shape of a. startswith
(prefix[, start, end])Returns a boolean array which is True where the string element in self starts with prefix, otherwise False. strip
([chars])For each element in self, return a copy with the leading and trailing characters removed. swapaxes
(axis1, axis2)Return a view of the array with axis1 and axis2 interchanged. swapcase
()For each element in self, return a copy of the string with uppercase characters converted to lowercase and vice versa. take
(indices[, axis, out, mode])Return an array formed from the elements of a at the given indices. title
()For each element in self, return a titlecased version of the string: words start with uppercase characters, all remaining cased characters are lowercase. tofile
(fid[, sep, format])Write array to a file as text or binary (default). tolist
()Return the array as a (possibly nested) list. tostring
([order])Construct Python bytes containing the raw data bytes in the array. translate
(table[, deletechars])For each element in self, return a copy of the string where all characters occurring in the optional argument deletechars are removed, and the remaining characters have been mapped through the given translation table. transpose
(*axes)Returns a view of the array with axes transposed. upper
()Return an array with the elements of self converted to uppercase. view
([dtype, type])New view of array with the same data. zfill
(width)Return the numeric string left-filled with zeros in a string of length width.