9 characters, and clashes with existing files.
32 def userNameToFileName(userName, existing=[], prefix="", suffix=""):  argument
36     upper- and lower-case characters, and clashes with existing files.
40             existing: A case-insensitive list of all existing file names.
130     if fullName.lower() in existing:
131         fullName = handleClash1(userName, existing, prefix, suffix)
136 def handleClash1(userName, existing=[], prefix="", suffix=""):  argument
138     existing should be a case-insensitive list
139     of all existing file names.
143     >>> existing = ["a" * 5]
145     >>> e = list(existing)
146     >>> handleClash1(userName="A" * 5, existing=e,
151     >>> e = list(existing)
153     >>> handleClash1(userName="A" * 5, existing=e,
158     >>> e = list(existing)
160     >>> handleClash1(userName="A" * 5, existing=e,
179         if fullName.lower() not in existing:
188         finalName = handleClash2(existing, prefix, suffix)
193 def handleClash2(existing=[], prefix="", suffix=""):  argument
195     existing should be a case-insensitive list
196     of all existing file names.
200     >>> existing = [prefix + str(i) + suffix for i in range(100)]
202     >>> e = list(existing)
203     >>> handleClash2(existing=e, prefix=prefix, suffix=suffix) == (
207     >>> e = list(existing)
209     >>> handleClash2(existing=e, prefix=prefix, suffix=suffix) == (
213     >>> e = list(existing)
215     >>> handleClash2(existing=e, prefix=prefix, suffix=suffix) == (
227         if fullName.lower() not in existing: