numpy.char.chararray#

classnumpy.char.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

Thechararray class exists for backwards compatibility withNumarray, it is not recommended for new development. Starting from numpy1.4, if one needs arrays of strings, it is recommended to use arrays ofdtypeobject_,bytes_ orstr_, and usethe free functions in thenumpy.char module for fast vectorizedstring operations.

Versus a NumPy array of dtypebytes_ orstr_, thisclass adds the following functionality:

1. values automatically have whitespace removed from the endwhen indexed

2. comparison operators automatically remove whitespace from theend when comparing values

3. vectorized string operations are provided as methods(e.g.endswith) and infix operators (e.g."+","*","%")

chararrays should be created usingnumpy.char.array ornumpy.char.asarray, rather than this constructor directly.

This constructor creates the array, usingbuffer (withoffsetandstrides) if it is notNone. Ifbuffer isNone, thenconstructs a new array withstrides in “C order”, unless bothlen(shape)>=2 andorder='F', in which casestridesis in “Fortran order”.

Parameters:

shapetuple

Shape of the array.

itemsizeint, optional

Length of each array element, in number of characters. Default is 1.

unicodebool, optional

Are the array elements of type unicode (True) or string (False).Default is False.

bufferobject exposing the buffer interface or str, optional

Memory address of the start of the array data. Default is None,in which case a new array is created.

offsetint, optional

Fixed stride displacement from the beginning of an axis?Default is 0. Needs to be >=0.

stridesarray_like of ints, optional

Strides for the array (seestrides forfull 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

Try it in your browser!

>>>importnumpyasnp>>>charar=np.char.chararray((3,3))>>>charar[:]='a'>>>chararchararray([[b'a', b'a', b'a'],           [b'a', b'a', b'a'],           [b'a', b'a', b'a']], dtype='|S1')

>>>charar=np.char.chararray(charar.shape,itemsize=5)>>>charar[:]='abc'>>>chararchararray([[b'abc', b'abc', b'abc'],           [b'abc', b'abc', b'abc'],           [b'abc', b'abc', b'abc']], dtype='|S5')

Go BackOpen In Tab

Attributes:

T

View of the transposed array.

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.

device

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.

itemset

itemsize

Length of one array element in bytes.

mT

View of the matrix transposed array.

nbytes

Total bytes consumed by the elements of the array.

ndim

Number of array dimensions.

newbyteorder

ptp

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 substringsub in the range [start,end].
decode([encoding, errors])	Callsbytes.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])	Callsstr.encode element-wise.
endswith(suffix[, start, end])	Returns a boolean array which isTrue where the string element inself ends withsuffix, otherwiseFalse.
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 substringsub 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])	Likefind, but raisesValueError 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 inself, 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 inself, 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 sequenceseq.
ljust(width[, fillchar])	Return an array with the elements ofself left-justified in a string of lengthwidth.
lower()	Return an array with the elements ofself converted to lowercase.
lstrip([chars])	For each element inself, return a copy with the leading characters removed.
nonzero()	Return the indices of the elements that are non-zero.
put(indices, values[, mode])	Seta.flat[n]=values[n] for alln in indices.
ravel([order])	Return a flattened array.
repeat(repeats[, axis])	Repeat elements of an array.
replace(old, new[, count])	For each element inself, return a copy of the string with all occurrences of substringold replaced bynew.
reshape(shape, /, *[, order, copy])	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 inself, return the highest index in the string where substringsub is found, such thatsub is contained within [start,end].
rindex(sub[, start, end])	Likerfind, but raisesValueError when the substringsub is not found.
rjust(width[, fillchar])	Return an array with the elements ofself right-justified in a string of lengthwidth.
rsplit([sep, maxsplit])	For each element inself, return a list of the words in the string, usingsep as the delimiter string.
rstrip([chars])	For each element inself, 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, respectively.
sort([axis, kind, order])	Sort an array in-place.
split([sep, maxsplit])	For each element inself, return a list of the words in the string, usingsep as the delimiter string.
splitlines([keepends])	For each element inself, return a list of the lines in the element, breaking at line boundaries.
squeeze([axis])	Remove axes of length one froma.
startswith(prefix[, start, end])	Returns a boolean array which isTrue where the string element inself starts withprefix, otherwiseFalse.
strip([chars])	For each element inself, return a copy with the leading and trailing characters removed.
swapaxes(axis1, axis2)	Return a view of the array withaxis1 andaxis2 interchanged.
swapcase()	For each element inself, 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 ofa at the given indices.
title()	For each element inself, 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 ana.ndim-levels deep nested list of Python scalars.
translate(table[, deletechars])	For each element inself, return a copy of the string where all characters occurring in the optional argumentdeletechars 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 ofself 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 lengthwidth.

tostring