Python 获取字符串中的最后一个子字符串？

如何获取最后一个子字符串“crop=400:704:440:8”字符串？我能想到的是使用rfind（“crop=”）来获取初始索引，但我不确定下一步该怎么做

我的解决方案：

[Parsed_cropdetect_0 @ 0x7f8ee9c22c60] x1:438 x2:841 y1:0 y2:718 w:400 h:704 x:440 y:8 pts:638638 t:10.643967 crop=400:704:440:8
[Parsed_cropdetect_0 @ 0x7f8ee9c22c60] x1:438 x2:841 y1:0 y2:718 w:400 h:704 x:440 y:8 pts:640640 t:10.677333 crop=400:704:440:8
[Parsed_cropdetect_0 @ 0x7f8ee9c22c60] x1:438 x2:841 y1:0 y2:718 w:400 h:704 x:440 y:8 pts:642642 t:10.710700 crop=400:704:440:8
[Parsed_cropdetect_0 @ 0x7f8ee9c22c60] x1:438 x2:841 y1:0 y2:718 w:400 h:704 x:440 y:8 pts:644644 t:10.744067 crop=400:704:440:8
[Parsed_cropdetect_0 @ 0x7f8ee9c22c60] x1:438 x2:841 y1:0 y2:718 w:400 h:704 x:440 y:8 pts:646646 t:10.777433 crop=400:704:440:8
[Parsed_cropdetect_0 @ 0x7f8ee9c22c60] x1:438 x2:841 y1:0 y2:718 w:400 h:704 x:440 y:8 pts:648648 t:10.810800 crop=400:704:440:8
[Parsed_cropdetect_0 @ 0x7f8ee9c22c60] x1:438 x2:841 y1:0 y2:718 w:400 h:704 x:440 y:8 pts:650650 t:10.844167 crop=400:704:440:8
frame=  326 fps=0.0 q=0.0 Lsize=N/A time=00:00:10.89 bitrate=N/A    
video:31kB audio:1876kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown

---

您可以使用awk打印第n列：

start =  output.rfind("crop=")
end =  output.find('\n', start, len(output))

print output[start:end]

可以使用以下语法筛选出至少没有14列的所有行：

awk '{print $14}' file

---

你试过使用正则表达式吗？我建议采用以下模式：

awk 'NF==14 {print $14}' file

---

您可以使用来构建自己的新字符串。

如果将这些行中的每一行作为单独的字符串，则可以提取该行的最后一个子字符串，如下所示：

((crop=)(\d|:)*(\d))

如果

然后使用

x = "crop=400:704:440:8"

---

它将返回字符串中的最后一个字符

您可以尝试下面的

re.findall

函数

x[-1]

---

您只需将

str.split

和

str.startswith

与索引一起使用即可

>>> import re
>>> s = """[Parsed_cropdetect_0 @ 0x7f8ee9c22c60] x1:438 x2:841 y1:0 y2:718 w:400 h:704 x:440 y:8 pts:638638 t:10.643967 crop=400:704:440:8
[Parsed_cropdetect_0 @ 0x7f8ee9c22c60] x1:438 x2:841 y1:0 y2:718 w:400 h:704 x:440 y:8 pts:640640 t:10.677333 crop=400:704:440:8
[Parsed_cropdetect_0 @ 0x7f8ee9c22c60] x1:438 x2:841 y1:0 y2:718 w:400 h:704 x:440 y:8 pts:642642 t:10.710700 crop=400:704:440:8
[Parsed_cropdetect_0 @ 0x7f8ee9c22c60] x1:438 x2:841 y1:0 y2:718 w:400 h:704 x:440 y:8 pts:644644 t:10.744067 crop=400:704:440:8
[Parsed_cropdetect_0 @ 0x7f8ee9c22c60] x1:438 x2:841 y1:0 y2:718 w:400 h:704 x:440 y:8 pts:646646 t:10.777433 crop=400:704:440:8
[Parsed_cropdetect_0 @ 0x7f8ee9c22c60] x1:438 x2:841 y1:0 y2:718 w:400 h:704 x:440 y:8 pts:648648 t:10.810800 crop=400:704:440:8
[Parsed_cropdetect_0 @ 0x7f8ee9c22c60] x1:438 x2:841 y1:0 y2:718 w:400 h:704 x:440 y:8 pts:650650 t:10.844167 crop=400:704:440:8
frame=  326 fps=0.0 q=0.0 Lsize=N/A time=00:00:10.89 bitrate=N/A    
video:31kB audio:1876kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown"""
>>> re.findall(r'crop=[\d:]+', s)[-1]
'crop=400:704:440:8'

---

如果您有索引和大小。您可以这样做

a[index:index+size]

@AshwaniDausodia最终裁剪后的数字将根据我输入的内容而变化。所以我不知道它们会有多大。数据似乎是

列表

而不是

字符串

请澄清你的问题？@VishnuUpadhyay这是一个字符串。。。

>>> import re
>>> s = """[Parsed_cropdetect_0 @ 0x7f8ee9c22c60] x1:438 x2:841 y1:0 y2:718 w:400 h:704 x:440 y:8 pts:638638 t:10.643967 crop=400:704:440:8
[Parsed_cropdetect_0 @ 0x7f8ee9c22c60] x1:438 x2:841 y1:0 y2:718 w:400 h:704 x:440 y:8 pts:640640 t:10.677333 crop=400:704:440:8
[Parsed_cropdetect_0 @ 0x7f8ee9c22c60] x1:438 x2:841 y1:0 y2:718 w:400 h:704 x:440 y:8 pts:642642 t:10.710700 crop=400:704:440:8
[Parsed_cropdetect_0 @ 0x7f8ee9c22c60] x1:438 x2:841 y1:0 y2:718 w:400 h:704 x:440 y:8 pts:644644 t:10.744067 crop=400:704:440:8
[Parsed_cropdetect_0 @ 0x7f8ee9c22c60] x1:438 x2:841 y1:0 y2:718 w:400 h:704 x:440 y:8 pts:646646 t:10.777433 crop=400:704:440:8
[Parsed_cropdetect_0 @ 0x7f8ee9c22c60] x1:438 x2:841 y1:0 y2:718 w:400 h:704 x:440 y:8 pts:648648 t:10.810800 crop=400:704:440:8
[Parsed_cropdetect_0 @ 0x7f8ee9c22c60] x1:438 x2:841 y1:0 y2:718 w:400 h:704 x:440 y:8 pts:650650 t:10.844167 crop=400:704:440:8
frame=  326 fps=0.0 q=0.0 Lsize=N/A time=00:00:10.89 bitrate=N/A    
video:31kB audio:1876kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown"""
>>> re.findall(r'crop=[\d:]+', s)[-1]
'crop=400:704:440:8'

a = """[Parsed_cropdetect_0 @ 0x7f8ee9c22c60] x1:438 x2:841 y1:0 y2:718 w:400 h:704 x:440 y:8 pts:638638 t:10.643967 crop=400:704:440:8
[Parsed_cropdetect_0 @ 0x7f8ee9c22c60] x1:438 x2:841 y1:0 y2:718 w:400 h:704 x:440 y:8 pts:640640 t:10.677333 crop=400:704:440:8
[Parsed_cropdetect_0 @ 0x7f8ee9c22c60] x1:438 x2:841 y1:0 y2:718 w:400 h:704 x:440 y:8 pts:642642 t:10.710700 crop=400:704:440:8
[Parsed_cropdetect_0 @ 0x7f8ee9c22c60] x1:438 x2:841 y1:0 y2:718 w:400 h:704 x:440 y:8 pts:644644 t:10.744067 crop=400:704:440:8
[Parsed_cropdetect_0 @ 0x7f8ee9c22c60] x1:438 x2:841 y1:0 y2:718 w:400 h:704 x:440 y:8 pts:646646 t:10.777433 crop=400:704:440:8
[Parsed_cropdetect_0 @ 0x7f8ee9c22c60] x1:438 x2:841 y1:0 y2:718 w:400 h:704 x:440 y:8 pts:648648 t:10.810800 crop=400:704:440:8
[Parsed_cropdetect_0 @ 0x7f8ee9c22c60] x1:438 x2:841 y1:0 y2:718 w:400 h:704 x:440 y:8 pts:650650 t:10.844167 crop=400:704:440:8
frame=  326 fps=0.0 q=0.0 Lsize=N/A time=00:00:10.89 bitrate=N/A    
video:31kB audio:1876kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown"""

for line in a.split('\n'):
    if line.split()[-1].startswith('crop'):
        print line.split()[-1] 


>>> 
crop=400:704:440:8
crop=400:704:440:8
crop=400:704:440:8
crop=400:704:440:8
crop=400:704:440:8
crop=400:704:440:8
crop=400:704:440:8