9.6 KiB
The N-dimensional array (ndarray)
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* TOC {:toc}The goal
Class has a very important job as a core container type in Python. It is really hard to find a good overview how to use them in a good practice manner.
Questions to David Rotermund
Chaining of (ndarray) methods
import numpy as np
a = np.ones((3, 3))
b = a.mean(axis=1).max()
print(b) # -> 1.0
numpy.ndarray.fill
Array methods
Array conversion
| ndarray.item(*args) | Copy an element of an array to a standard Python scalar and return it. |
| ndarray.tolist() | Return the array as an a.ndim-levels deep nested list of Python scalars. |
| ndarray.itemset(*args) | Insert scalar into an array (scalar is cast to array's dtype, if possible) |
| ndarray.tostring([order]) | A compatibility alias for tobytes, with exactly the same behavior. |
| ndarray.tobytes([order]) | Construct Python bytes containing the raw data bytes in the array. |
| ndarray.tofile(fid[, sep, format]) | Write array to a file as text or binary (default). |
| ndarray.dump(file) | Dump a pickle of the array to the specified file. |
| ndarray.dumps() | Returns the pickle of the array as a string. |
| ndarray.astype(dtype[, order, casting, ...]) | Copy of the array, cast to a specified type. |
| ndarray.byteswap([inplace]) | Swap the bytes of the array elements |
| ndarray.copy([order]) | Return a copy of the array. |
| ndarray.view([dtype][, type]) | New view of array with the same data. |
| ndarray.getfield(dtype[, offset]) | Returns a field of the given array as a certain type. |
| ndarray.setflags([write, align, uic]) | Set array flags WRITEABLE, ALIGNED, WRITEBACKIFCOPY, respectively. |
| ndarray.fill(value) | Fill the array with a scalar value. |
Shape manipulation
|ndarray.reshape(shape[, order])| Returns an array containing the same data with a new shape.
|ndarray.resize(new_shape[, refcheck])| Change shape and size of array in-place.
|ndarray.transpose(*axes)| Returns a view of the array with axes transposed.
|ndarray.swapaxes(axis1, axis2)| Return a view of the array with axis1 and axis2 interchanged.
|ndarray.flatten([order])| Return a copy of the array collapsed into one dimension.
|ndarray.ravel([order])| Return a flattened array.
|ndarray.squeeze([axis])| Remove axes of length one from a.
Item selection and manipulation
|ndarray.take(indices[, axis, out, mode])| Return an array formed from the elements of a at the given indices.
|ndarray.put(indices, values[, mode])| Set a.flat[n] = values[n] for all n in indices.
|ndarray.repeat(repeats[, axis])| Repeat elements of an array.
|ndarray.choose(choices[, out, mode])| Use an index array to construct a new array from a set of choices.
|ndarray.sort([axis, kind, order])| Sort an array in-place.
|ndarray.argsort([axis, kind, order])| Returns the indices that would sort this array.
|ndarray.partition(kth[, axis, kind, order])| Rearranges the elements in the array in such a way that the value of the element in kth position is in the position it would be in a sorted array.
|ndarray.argpartition(kth[, axis, kind, order])| Returns the indices that would partition this array.
|ndarray.searchsorted(v[, side, sorter])| Find indices where elements of v should be inserted in a to maintain order.
|ndarray.nonzero()| Return the indices of the elements that are non-zero.
|ndarray.compress(condition[, axis, out])| Return selected slices of this array along given axis.
|ndarray.diagonal([offset, axis1, axis2])| Return specified diagonals.
Calculation
|ndarray.max([axis, out, keepdims, initial, ...])| Return the maximum along a given axis.
|ndarray.argmax([axis, out, keepdims])| Return indices of the maximum values along the given axis.
|ndarray.min([axis, out, keepdims, initial, ...])| Return the minimum along a given axis.
|ndarray.argmin([axis, out, keepdims])| Return indices of the minimum values along the given axis.
|ndarray.ptp([axis, out, keepdims])| Peak to peak (maximum - minimum) value along a given axis.
|ndarray.clip([min, max, out])| Return an array whose values are limited to [min, max].
|ndarray.conj()| Complex-conjugate all elements.
|ndarray.round([decimals, out])| Return a with each element rounded to the given number of decimals.
|ndarray.trace([offset, axis1, axis2, dtype, out])| Return the sum along diagonals of the array.
|ndarray.sum([axis, dtype, out, keepdims, ...])| Return the sum of the array elements over the given axis.
|ndarray.cumsum([axis, dtype, out])| Return the cumulative sum of the elements along the given axis.
|ndarray.mean([axis, dtype, out, keepdims, where])| Returns the average of the array elements along given axis.
|ndarray.var([axis, dtype, out, ddof, ...])| Returns the variance of the array elements, along given axis.
|ndarray.std([axis, dtype, out, ddof, ...])| Returns the standard deviation of the array elements along given axis.
|ndarray.prod([axis, dtype, out, keepdims, ...])| Return the product of the array elements over the given axis
|ndarray.cumprod([axis, dtype, out])| Return the cumulative product of the elements along the given axis.
|ndarray.all([axis, out, keepdims, where])| Returns True if all elements evaluate to True.
|ndarray.any([axis, out, keepdims, where])| Returns True if any of the elements of a evaluate to True.
Arithmetic, matrix multiplication, and comparison operations
|ndarray.__lt__(value, /)| Return self<value.
|ndarray.__le__(value, /)| Return self<=value.
|ndarray.__gt__(value, /)| Return self>value.
|ndarray.__ge__(value, /)| Return self>=value.
|ndarray.__eq__(value, /)| Return self==value.
|ndarray.__ne__(value, /)| Return self!=value.
|ndarray.__bool__(/)| True if self else False
|ndarray.__neg__(/)| -self
|ndarray.__pos__(/)| +self
|ndarray.__abs__(self)|
|ndarray.__invert__(/)| ~self
|ndarray.__add__(value, /)| Return self+value.
|ndarray.__sub__(value, /)| Return self-value.
|ndarray.__mul__(value, /)| Return self*value.
|ndarray.__truediv__(value, /)| Return self/value.
|ndarray.__floordiv__(value, /)| Return self//value.
|ndarray.__mod__(value, /)| Return self%value.
|ndarray.__divmod__(value, /)| Return divmod(self, value).
|ndarray.__pow__(value[, mod])| Return pow(self, value, mod).
|ndarray.__lshift__(value, /)| Return self<<value.
|ndarray.__rshift__(value, /)| Return self>>value.
|ndarray.__and__(value, /)| Return self&value.
|ndarray.__or__(value, /)| Return self|value.
|ndarray.__xor__(value, /)| Return self^value.
|ndarray.__iadd__(value, /)| Return self+=value.
|ndarray.__isub__(value, /)| Return self-=value.
|ndarray.__imul__(value, /)| Return self*=value.
|ndarray.__itruediv__(value, /)| Return self/=value.
|ndarray.__ifloordiv__(value, /)| Return self//=value.
|ndarray.__imod__(value, /)| Return self%=value.
|ndarray.__ipow__(value, /)| Return self**=value.
|ndarray.__ilshift__(value, /)| Return self<<=value.
|ndarray.__irshift__(value, /)| Return self>>=value.
|ndarray.__iand__(value, /)| Return self&=value.
|ndarray.__ior__(value, /)| Return self|=value.
|ndarray.__ixor__(value, /)| Return self^=value.
|ndarray.__matmul__(value, /)| Return self@value.