Numpy数组存储含%多行字符串为空问题排查

用np.empty(1, dtype=str)创建数组时，numpy默认会生成长度为0的字符串数组（dtype='<U0'），赋值时会自动截断为空字符串，和%字符无关。

有两种可靠的处理方式：

方法1：指定dtype=object #

用object类型存储字符串，不会限制长度，适配任意长度的文本内容：

import numpy as np

strings = np.empty(1, dtype=object)
strings[0] = """         $_1 = 
    %_1.a =      25129 ± 92.3741
    $_2 = %_2.height =    11340.5 ± 1951.81
    $_3 = %_2.center =    63.4979 ± 0.275278
      $_4 = %_2.hwhm =     1.6318 ± 0.324661
    $_5 = %_3.height =    19482.3 ± 2420.92
    $_6 = %_3.center =    106.329 ± 0.12973
      $_7 = %_3.hwhm =    1.07347 ± 0.155327
    $_8 = %_4.height =    9985.67 ± 2382.35
    $_9 = %_4.center =    223.417 ± 0.257358
     $_10 = %_4.hwhm =   -1.11065 ± 0.30902
   $_11 = %_5.height =      61622 ± 2154.58
   $_12 = %_5.center =    443.983 ± 0.0458769
     $_13 = %_5.hwhm =      1.338 ± 0.0540433
   $_14 = %_6.height =    36949.9 ± 2230.42
   $_15 = %_6.center =    541.081 ± 0.0738621
     $_16 = %_6.hwhm =    1.24646 ± 0.086812
   $_17 = %_7.height =    28368.8 ± 2217.38
   $_18 = %_7.center =    693.312 ± 0.0968789
     $_19 = %_7.hwhm =    1.26497 ± 0.114331"""

print(strings[0])

方法2：指定足够长度的字符串类型 #

如果不想用object类型，可以显式指定字符串的最大长度（比如U1000，确保能容纳目标多行字符串）：

import numpy as np

strings = np.empty(1, dtype='U1000')
strings[0] = """         $_1 = 
    %_1.a =      25129 ± 92.3741
    $_2 = %_2.height =    11340.5 ± 1951.81
    $_3 = %_2.center =    63.4979 ± 0.275278
      $_4 = %_2.hwhm =     1.6318 ± 0.324661
    $_5 = %_3.height =    19482.3 ± 2420.92
    $_6 = %_3.center =    106.329 ± 0.12973
      $_7 = %_3.hwhm =    1.07347 ± 0.155327
    $_8 = %_4.height =    9985.67 ± 2382.35
    $_9 = %_4.center =    223.417 ± 0.257358
     $_10 = %_4.hwhm =   -1.11065 ± 0.30902
   $_11 = %_5.height =      61622 ± 2154.58
   $_12 = %_5.center =    443.983 ± 0.0458769
     $_13 = %_5.hwhm =      1.338 ± 0.0540433
   $_14 = %_6.height =    36949.9 ± 2230.42
   $_15 = %_6.center =    541.081 ± 0.0738621
     $_16 = %_6.hwhm =    1.24646 ± 0.086812
   $_17 = %_7.height =    28368.8 ± 2217.38
   $_18 = %_7.center =    693.312 ± 0.0968789
     $_19 = %_7.hwhm =    1.26497 ± 0.114331"""

print(strings[0])

运行上述任意一种代码，都会完整输出目标多行字符串，%字符不会造成任何影响——之前的空输出完全是因为numpy默认创建的字符串数组长度为0导致的截断。

内容的提问来源于stack exchange，提问作者srtgvinuhl