NumPy:漂亮的打印表格数据

Question

我想打印NumPy表格数组数据,以便它看起来不错.R和数据库控制台似乎表现出很好的能力.但是,NumPy的表格数组的内置打印看起来像垃圾:

import numpy as np
dat_dtype = {
    'names' : ('column_one', 'col_two', 'column_3'),
    'formats' : ('i', 'd', '|S12')}
dat = np.zeros(4, dat_dtype)
dat['column_one'] = range(4)
dat['col_two'] = 10**(-np.arange(4, dtype='d') - 4)
dat['column_3'] = 'ABCD'
dat['column_3'][2] = 'long string'

print(dat)
# [(0, 0.0001, 'ABCD') (1, 1.0000000000000001e-005, 'ABCD')
#  (2, 9.9999999999999995e-007, 'long string')
#  (3, 9.9999999999999995e-008, 'ABCD')]

print(repr(dat))
# array([(0, 0.0001, 'ABCD'), (1, 1.0000000000000001e-005, 'ABCD'),
#        (2, 9.9999999999999995e-007, 'long string'),
#        (3, 9.9999999999999995e-008, 'ABCD')], 
#       dtype=[('column_one', '<i4'), ('col_two', '<f8'), ('column_3', '|S12')])

我希望看起来更像数据库吐出的东西,例如postgres风格:

 column_one | col_two |  column_3
------------+---------+-------------
          0 |  0.0001 | ABCD
          1 |  1e-005 | long string
          2 |  1e-008 | ABCD
          3 |  1e-007 | ABCD

是否有任何好的第三方Python库来格式化漂亮的ASCII表？

我使用的是Python 2.5,NumPy 1.3.0.

Answer 1

我似乎有很好的输出和漂亮:

from prettytable import PrettyTable
x = PrettyTable(dat.dtype.names)
for row in dat:
    x.add_row(row)
# Change some column alignments; default was 'c'
x.align['column_one'] = 'r'
x.align['col_two'] = 'r'
x.align['column_3'] = 'l'

而且输出也不错.在border其他几个选项中甚至还有一个开关:

>>> print(x)
+------------+---------+-------------+
| column_one | col_two |   column_3  |
+------------+---------+-------------+
|          0 |  0.0001 | ABCD        |
|          1 |  1e-005 | ABCD        |
|          2 |  1e-006 | long string |
|          3 |  1e-007 | ABCD        |
+------------+---------+-------------+
>>> print(x.get_string(border=False))
 column_one  col_two    column_3  
          0   0.0001  ABCD        
          1   1e-005  ABCD        
          2   1e-006  long string 
          3   1e-007  ABCD        

Answer 2

该tabulate包适用于Numpy数组:

import numpy as np
from tabulate import tabulate

m = np.array([[1, 2, 3], [4, 5, 6]])
headers = ["col 1", "col 2", "col 3"]

# tabulate data
table = tabulate(m, headers, tablefmt="fancy_grid")

# output
print(table)

(上面的代码是Python 3;对于Python 2,from __future__ import print_function在脚本顶部添加)

输出:

???????????????????????????????
?   col 1 ?   col 2 ?   col 3 ?
???????????????????????????????
?       1 ?       2 ?       3 ?
???????????????????????????????
?       4 ?       5 ?       6 ?
???????????????????????????????

该软件包通过pip以下方式安装

$ pip install tabulate     # (use pip3 for Python 3 on some systems)

Answer 3

你可以利用数组理解并使用printf格式字符串:

for c1, c2, c3 in dat:  
    print "%2f | %8e | %s" % (c1, c2, c3)

https://en.wikipedia.org/wiki/Printf_format_string
如果你达到2.7版本,你可以获得更多自定义

Answer 4

您可能想要查看Pandas,它有很多很好的功能来处理表格数据,并且似乎在打印时更好地处理(它被设计为R的python替代品):

http://pandas.pydata.org/