[Edit: Finished code at the end of this post.]
Hey guys!,
I'm in the middle of writing a class that allows for more flexible string usage in Python (yes, it's possible).
Although Python implements strings extremely well, it's missing string mutation.
It seems as though the developers chose not to implement it (even in py3k), though for what reason, I do not know.
My problem is this; how do you re-assign the value of an object (from within the scope of a function) in a class (that inherits string properties)?
To simplify;
(class) -> string object
(class) - (function) -> modify string object
The goal is not to mutate the object (that's impossible), the goal is to re-assign the value attributed to the object.
Here is an outline;
PHP Code:
class semi_mutable_str (str):
# define a class that inherits native str properties
def __init__(self, value):
self.str = value
def rm(self, pos):
'''Remove the character in self.str at pos.'''
new = self.str[0:pos]
new += self.str[pos+1:len(self.str)]
self.str = new
del new
return self.str
>>> variable = semi_mutable_str ("aaa aba abb bbb b a")
>>> variable
"aaa aba abb bbb b a"
>>> variable.rm(0)
>>> variable.str
"aa aba abb bbb b a"
>>> variable
"aaa aba abb bbb b a"
Note that variable.str has been appropriately changed, but when I call variable, I get what I started with.
How do I change the value that is returned when I call 'variable'?
That is my question.
Thank you very much for reading, and your time.
Regards
EDIT -> Finished Class:
Code:
#!/usr/bin/env python
# Mutable strings meet Python 2.x.
# v.1.3 - vminch@gmail.com
# A very big thank-you to Lster and boblemur on Ubuntuforums!
# Because of their advice, I could piece together some hackery
# at the end to make this all work!
# Member Functions:
# rm
# rm_phr
# purge
# asgn
# asgn_r
# set
# set_phr
# Please read the documentation in each function for details, or email me.
class m_str(str):
'''m_str is a Python 2.x class created to extend the uses of string objects.
It inherits all of the str class's properties as well! :D.
'''
def __init__(self, content):
'''Initialize the m_str.'''
self.str = content
def rm(self, pos):
'''Remove the character in self.str at pos (position).
Note: m_str(s) start indexing at 0.
'''
new = self.str[0:pos]+self.str[pos+1:len(self.str)]
self.str = new
del new
return self.str
def rm_phr(self, phr, new=""):
'''Remove ALL INSTANCES of phr or char (phrase) from self.str. Leaves whitespace.
To remove whitespace, simply obj.rm_phr(' ')
'''
lphr=len(phr)
if phr in self.str:
loc = self.str.find(phr)
self.str = self.purge(loc, lphr)
loc = self.str.find(phr)
self.rm_phr(phr=phr, new=new)
else:
return self.str
def purge(self, loc, lphr):
'''Helpher function to the recursive self.rm_phr.
Removes a chunk of self.str that
starts at loc (location) is lphr (lenght of phrase) long.
'''
if loc == 0:
new = self.str[lphr:len(self.str)]
else:
new = self.str[0:loc]+self.str[loc+lphr:len(self.str)]
return new
def asgn(self, phr, pos=0):
'''Assign char/phr to self.str at pos.
The existing char will be SCOOTED TO THE RIGHT.'''
if pos == 0:
new = phr+self.str
else:
new = self.str[0:pos]+phr+self.str[pos:len(self.str)]
self.str = new
del new
return self.str
def asgn_r(self, phr):
'''Assign char/phr to self.str to the right side of the string.'''
self.asgn(phr, pos=len(self.str))
return self.str
def set(self, pos, char):
'''Set pos in self.str to char.
The existing char will be deleted.
'''
if len(char) != 1:
return self.str
if pos == 0:
new = char+self.str[1:len(self.str)]
if pos > 0:
new = self.str[0:pos]+char+self.str[pos+1:len(self.str)]
self.str = new
del new
return self.str
def set_phr(self, pos, phr):
'''Set pos:lphr in self.str to phr.
The existing phr will be deleted.
'''
lphr = len(phr)
if pos == 0:
new = phr+self.str[lphr:len(self.str)]
if pos > 0:
new = self.str[0:pos]+phr+self.str[pos+lphr:len(self.str)]
self.str = new
del new
return self.str
def __str__(self):
return self.str
Adv Reply
Originally Posted by Glaxed
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