![](/img/trans.png)
[英]"NoneType" Object has no attribute error by python linkedinapi
[英]Python - Attribute error, 'NoneType' object has no attribute
因此,我有一个程序,该程序可以推理出行文件并向stderr输出任何错误。
for line in lines_file:
#get offset up to start of coordinates
start = re.compile('\s*line\s*')
m = start.match(line)
offset = m.end()
try:
for i in range(4):
xy = re.compile('\s*([-]?[0-9]{1,3})\s*')
if xy.match(line,offset):
m = xy.match(line,offset)
else:
raise Exception
coordinate = m.group(1)
if int(coordinate) > 250 or int(coordinate) < -250:
raise Exception
offset = m.end()
end = re.compile('\s*$')
if not end.match(line,offset):
raise Exception
except Exception as e:
print >> sys.stderr, 'Error in line ' + str(line_number) + ":"
print >> sys.stderr, " " * 4 + line,
print >> sys.stderr, " " * (offset + 4) + "^"
line_number = line_number + 1
continue
如果我输入了无效的输入行,希望将无效的行打印到stderr,我得到的输出是:
Traceback (most recent call last):
File "lines_to_svg.py", line 37, in <module>
offset = m.end()
AttributeError: 'NoneType' object has no attribute 'end'
因为这是我代码的一部分,所以第37行是offset = m.end()
。 那么,为什么我总是收到属性错误? 这是上面的for循环之前的代码,以防万一这会导致错误:
import sys
import re
# SVG header with placeholders for canvas width and height
SVG_HEADER = "<svg xmlns=\"http:#www.w3.org/2000/svg\" version=\"1.1\""" width=\"%d\" height=\"%d\">\n"
# SVG bounding box with placeholders for width and height
SVG_BOUNDING_BOX = "<rect x=\"0\" y=\"0\" width=\"%d\" height=\"%d\""" style=\"stroke:#000;fill:none\" />\n"
# SVG line with placeholders for x0, y0, x1, y1
SVG_LINE = "<line x1=\"%d\" y1=\"%d\" x2=\"%d\" y2=\"%d\""" style=\"stroke:#000\" />\n"
# SVG footer
SVG_FOOTER = "</svg>"
CANVAS_HEIGHT = 500
CANVAS_WIDTH = 500
# process command line arguments
if len(sys.argv) != 2:
print >> sys.stderr, "Usage:", str(sys.argv[0]), "lines_file"
exit(1)
#open file for reading
try:
lines_file = open(sys.argv[1], 'r')
except IOError:
print >> sys.stderr, "Cannot open:", str(sys.argv[1])
exit(2)
offset = 0
line_number = 1
问题是offset = m.end()
但我似乎无法弄清楚为什么这会导致错误。
如果找不到匹配项,则re.match
返回None。 在这种情况下,您需要检查if m is None
。
您的代码中有两行offset = m.end()
。 问题必须在这里:
m = start.match(line)
offset = m.end()
因为另一行正在try
- except
块。
您可以将其更改为:
m = start.match(line)
if m is not None:
offset = m.end()
如果没有匹配项,则保留旧的偏移量,即m
为None
。
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.