ValueError: zero length field name in format python
PythonFormatPython Problem Overview
> Possible Duplicate:
> “ValueError: zero length field name in format” error in Python 3.0,3.1,3.2
I have spent hours trying to solve this problem but to no avail. I read this guide. I haven't found any examples how to do what I need.
When I run the script I get this error (partly omitted):
Traceback (...):
[...]
output.write("{: > 026,.18e} {: > 026,.18e}\n".format(x,y))
ValueError: zero length field name in format.
The code is written in python 2.6 or 2.7 but I run python 3.1. How would I need to change output format so that it would work?
def f(x,y,a = 0.01):
return y/(a+x)-y**3
def ekspEuler(N,dat):
output = open(dat,"w")
h = 3.0/N
x,y = 0,1 #zac.pogoj
for i in range(1,N+2):
output.write("{: > 026,.18e} {: > 026,.18e}\n".format(x,y))
y += h*f(x,y)
x = i*h
output.close()
Thanks for your help.
Python Solutions
Solution 1 - Python
Chances are that you're running an old Python version, and not 3.1. In Python 2.6, you need indices in the format specs, like this:
"{0} {1}\n".format(x,y)
Update your Python version to a recent one, preferably 2.7 or 3.2, to fix the problem. According to the documentation, leaving out the numeric indices http://docs.python.org/dev/library/string.html#format-string-syntax">should work in Python 3.1:
> Changed in version 3.1: The positional argument specifiers can be omitted, so '{} {}' is equivalent to '{0} {1}'.