獲取字符串中的最后一個子字符串？

Question

[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

您將如何獲得最后一個子字符串“ crop = 400：704：440：8”字符串？ 我能想到的是使用rfind（“ crop =”）來獲取初始索引，但是我不確定下一步該怎么做？

我的解決方案：

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

print output[start:end]

Answer 1

您可以嘗試下面的re.findall函數。

>>> 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'

Answer 2

您可以將str.split和str.startswith與索引str.startswith使用。

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

Answer 3

您可以使用awk打印第n列：

awk '{print $14}' file

您可以使用以下語法過濾掉沒有至少14列的所有行：

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

Answer 4

您是否嘗試過使用正則表達式？ 我建議模式：

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

您可以使用http://regex101.com/構建自己的新網站。

Answer 5

如果您將每行都作為單獨的字符串，則可以將該行的最后一個子字符串提取為：

# STRING FOR THAT LINE
s = """[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"""

# EXTRACT LAST SUBSTRING
s.split()[-1]

Answer 6

如果

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

然后使用

x[-1]

它將返回字符串中的最后一個字符