從陣列（扁平）列表建立記錄陣列並在 Numpy 中使用名稱獲取陣列

要從陣列（扁平）列表建立記錄陣列，請在 Python Numpy 中使用 **numpy.core.records.fromarrays()** 方法。名稱使用 **"names"** 引數設定。欄位名稱，可以以 'col1, col2, col3' 形式的逗號分隔字串的形式指定，也可以以 ['col1', 'col2', 'col3'] 形式的字串列表或元組的形式指定。可以使用空列表，在這種情況下使用預設欄位名稱（'f0'，'f1'，…）。

它返回由給定 arrayList 列組成的記錄陣列。第一個引數是陣列類物件（如列表、元組和 ndarray）的列表。dtype 是所有陣列的有效 dtype。格式、名稱、標題、對齊、位元組序引數，如果 dtype 為 None，則將這些引數傳遞給 numpy.format_parser 以構造 dtype。

步驟

首先，匯入所需的庫 -

import numpy as np

使用 numpy.array() 方法建立一個新陣列 -

arr1 = np.array([[5, 10, 15], [20, 25, 30]])
arr2 = np.array([[9, 18, 24], [87.5, 65, 23.8]])
arr3 = np.array([['12', 'bbb', 'john'], ['5.6', '29', 'k']])

顯示陣列 -

print("Array1...
",arr1)
print("Array2...
",arr2)
print("Array3...
",arr3)

獲取陣列的型別 -

print("
Array1 type...
", arr1.dtype)
print("
Array2 type...
", arr2.dtype)
print("
Array3 type...
", arr3.dtype)

獲取陣列的維度 -

print("
Array1 Dimensions...
", arr1.ndim)
print("
Array2 Dimensions...
", arr2.ndim)
print("
Array3 Dimensions...
", arr3.ndim)

要從陣列（扁平）列表建立記錄陣列，請在 Python Numpy 中使用 numpy.core.records.fromarrays() 方法。名稱使用 "names" 引數設定 -

rec = np.core.records.fromarrays([arr1,arr2,arr3], names = 'i,j,k')
print("
Record Array...
",rec)

根據名稱獲取陣列 -

print("
Fetching the array1...
",rec.i)
print("
Fetching the array2...
",rec.j)
print("
Fetching the array3...
",rec.k)

示例

import numpy as np

# Create a new array using the numpy.array() method
arr1 = np.array([[5, 10, 15], [20, 25, 30]])
arr2 = np.array([[9, 18, 24], [87.5, 65, 23.8]])
arr3 = np.array([['12', 'bbb', 'john'], ['5.6', '29', 'k']])

# Display the arrays
print("Array1...
",arr1)
print("Array2...
",arr2)
print("Array3...
",arr3)

# Get the type of the arrays
print("
Array1 type...
", arr1.dtype)
print("
Array2 type...
", arr2.dtype)
print("
Array3 type...
", arr3.dtype)

# Get the dimensions of the Arrays
print("
Array1 Dimensions...
", arr1.ndim)
print("
Array2 Dimensions...
", arr2.ndim)
print("
Array3 Dimensions...
", arr3.ndim)

# To create a record array from a (flat) list of array, use the numpy.core.records.fromarrays() method in Python Numpy
# The names is set using the "names" parameter
# The field names, either specified as a comma-separated string in the form 'col1, col2, col3', or as a list or tuple of strings in the form ['col1', 'col2', 'col3'].
# An empty list can be used, in that case default field names (‘f0’, ‘f1’, …) are used.
rec = np.core.records.fromarrays([arr1,arr2,arr3], names = 'i,j,k')
print("
Record Array...
",rec)

# Fetching the arrays based on names
print("
Fetching the array1...
",rec.i)
print("
Fetching the array2...
",rec.j)
print("
Fetching the array3...
",rec.k)

輸出

Array1...
[[ 5 10 15]
[20 25 30]]
Array2...
[[ 9. 18. 24. ]
[87.5 65. 23.8]]
Array3...
[['12' 'bbb' 'john']
['5.6' '29' 'k']]

Array1 type...
int64

Array2 type...
float64

Array3 type...
<U4

Array1 Dimensions...
2

Array2 Dimensions...
2

Array3 Dimensions...
2

Record Array...
[[( 5, 9. , '12') (10, 18. , 'bbb') (15, 24. , 'john')]
[(20, 87.5, '5.6') (25, 65. , '29') (30, 23.8, 'k')]]

Fhing the array1...
[[ 5 10 15]
[20 25 30]]

Fhing the array2...
[[ 9. 18. 24. ]
[87.5 65. 23.8]]

Fhing the array3...
[['12' 'bbb' 'john']
['5.6' '29' 'k']]

AmitDiwan

更新於: 2022-02-17

128 次檢視

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