Question

Consider the below piece of code:

searchList=["hello", "hello world", "world"]
pattern = 'hell'
matchingList = [t for t in searchList if re.match(pattern, t)]

The above code works fine in Jython 2.4.3 but fails in lower versions of Jython with this error:

ValueError: iterator indices must be consecutive ints starting at 0

Any workarounds?

With this below work around, am gettign the same error:

  for t in searchList:
      if re.match(pattern, t):
          matchingList.append(t)

Error seen in Jython 2.1

Answer 1

The code works fine on cpython 2.3.5, 2.2.3, 2.1.3, and 2.0 as well as jython 2.2.1, 2.2, and 2.1. List comprehensions are only available in 2.0+. Instead, you can write:

# Warning: This code is unnecessarily complex because of cpython 1.x (!) support
import re
searchList=["hello", "hello world", "world"]
pattern = 'hell'
matchingList = []
for t in searchList:
    if re.match(pattern, t):
        matchingList.append(t)

That being said, even 2.4 is ancient and has been unsupported for quite a while (this means that you must manually apply and adapt all security patches since then to have a secure system). The Python versions you’re catering to are more than a decade old, and almost certainly riddled with security vulnerabilities. Consider deprecating Python 2.5 and older.