replace() string in python

Question

I want to remove ">>> " and "... " form the doc using replace() but its not working for me (it prints the same doc). Check the last three lines of code.

doc = """
>>> from sets import Set
>>> engineers = Set(['John', 'Jane', 'Jack', 'Janice'])
>>> programmers = Set(['Jack', 'Sam', 'Susan', 'Janice'])
>>> managers = Set(['Jane', 'Jack', 'Susan', 'Zack'])
>>> employees = engineers | programmers | managers           # union
>>> engineering_management = engineers & managers            # intersection
>>> fulltime_management = managers - engineers - programmers # difference
>>> engineers.add('Marvin')                                  # add element
>>> print engineers 
Set(['Jane', 'Marvin', 'Janice', 'John', 'Jack'])
>>> employees.issuperset(engineers)     # superset test
False
>>> employees.update(engineers)         # update from another set
>>> employees.issuperset(engineers)
True
>>> for group in [engineers, programmers, managers, employees]: 
...     group.discard('Susan')          # unconditionally remove element
...     print group
...
Set(['Jane', 'Marvin', 'Janice', 'John', 'Jack'])
Set(['Janice', 'Jack', 'Sam'])
Set(['Jane', 'Zack', 'Jack'])
Set(['Jack', 'Sam', 'Jane', 'Marvin', 'Janice', 'John', 'Zack'])
"""

doc.replace(">>> ","")
doc.replace("...     ","")
print doc

So, can any one give a better solution for removing ">>> " and "... ".

Ashwini Chaudhary · Accepted Answer · 2013-06-16 11:13:58Z

7

Strings are immutable in python, so str.replace(and all other operations) simply return a new string and the original one is not affected at all:

doc = doc.replace(">>> ","")      # assign the new string back to `doc`
doc = doc.replace("...     ","")

help on str.replace:

>>> print str.replace.__doc__
S.replace(old, new[, count]) -> string

Return a copy of string S with all occurrences of substring old replaced by new. If the optional argument count is given, only the first count occurrences are replaced.

edited Jun 16, 2013 at 11:13

answered Jun 16, 2013 at 10:34

Ashwini Chaudhary

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1 Comment

georg Over a year ago

although this answer solves the OP's particular problem, in general replace is a wrong tool for that (think >>> print ">>>foo").

Alexander Tobias Bockstaller · Accepted Answer · 2013-06-16 10:34:36Z

3

replace() does not modify the string, it returns a new string with the modification.

So write: doc = doc.replace(">>> ","")

answered Jun 16, 2013 at 10:34

Alexander Tobias Bockstaller

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Comments

jamylak · Accepted Answer · 2013-06-16 11:27:58Z

1

Python strings are immutable so .replace returns a new string instead of mutating the original as you have presumed.

doc = doc.replace(">>> ","").replace("...     ","")
print doc

edited Jun 16, 2013 at 11:27

answered Jun 16, 2013 at 10:34

jamylak

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1 Comment

jamylak Over a year ago

@BurhanKhalid Ok fixed but I would have changed it happily without the DV ;) Also you are always free to edit things such as that in. IIRC that is not a valid reason to downvote since my answer is and was useful but no hard feelings here

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