numpy.array2string(a, max_line_width=None, precision=None, suppress_small=None, separator=' ', prefix='', style=<built-in function repr>, formatter=None)[source]

Return a string representation of an array.


a : ndarray

Input array.

max_line_width : int, optional

The maximum number of columns the string should span. Newline characters splits the string appropriately after array elements.

precision : int, optional

Floating point precision. Default is the current printing precision (usually 8), which can be altered using set_printoptions.

suppress_small : bool, optional

Represent very small numbers as zero. A number is “very small” if it is smaller than the current printing precision.

separator : str, optional

Inserted between elements.

prefix : str, optional

An array is typically printed as:

'prefix(' + array2string(a) + ')'

The length of the prefix string is used to align the output correctly.

style : function, optional

A function that accepts an ndarray and returns a string. Used only when the shape of a is equal to (), i.e. for 0-D arrays.

formatter : dict of callables, optional

If not None, the keys should indicate the type(s) that the respective formatting function applies to. Callables should return a string. Types that are not specified (by their corresponding keys) are handled by the default formatters. Individual types for which a formatter can be set are:

- 'bool'
- 'int'
- 'timedelta' : a `numpy.timedelta64`
- 'datetime' : a `numpy.datetime64`
- 'float'
- 'longfloat' : 128-bit floats
- 'complexfloat'
- 'longcomplexfloat' : composed of two 128-bit floats
- 'numpystr' : types `numpy.string_` and `numpy.unicode_`
- 'str' : all other strings

Other keys that can be used to set a group of types at once are:

- 'all' : sets all types
- 'int_kind' : sets 'int'
- 'float_kind' : sets 'float' and 'longfloat'
- 'complex_kind' : sets 'complexfloat' and 'longcomplexfloat'
- 'str_kind' : sets 'str' and 'numpystr'

array_str : str

String representation of the array.



if a callable in formatter does not return a string.


If a formatter is specified for a certain type, the precision keyword is ignored for that type.

This is a very flexible function; array_repr and array_str are using array2string internally so keywords with the same name should work identically in all three functions.


>>> x = np.array([1e-16,1,2,3])
>>> print(np.array2string(x, precision=2, separator=',',
...                       suppress_small=True))
[ 0., 1., 2., 3.]
>>> x  = np.arange(3.)
>>> np.array2string(x, formatter={'float_kind':lambda x: "%.2f" % x})
'[0.00 1.00 2.00]'
>>> x  = np.arange(3)
>>> np.array2string(x, formatter={'int':lambda x: hex(x)})
'[0x0L 0x1L 0x2L]'

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