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Python

Posted by Robert Meador
Robert Meador
1,844 Points

Need help converting a string to a list, deleting, then converting back to an intelligible string.

Kenneth mentions in one of the early Python videos that in order to delete something from a string using this method, you must convert to a list, delete, then convert back to a string. I tried this and it worked, but my final string looks terrible because everything's broken into individual characters (like a list...)

How could I clean this up?

myString = 'I shall delete X from this sentence'

myString 'I shall delete X from this sentence'

myList = list(myString)

myList ['I', ' ', 's', 'h', 'a', 'l', 'l', ' ', 'd', 'e', 'l', 'e', 't', 'e', ' ', 'X', ' ', 'f', 'r', 'o', 'm', ' ', 't', 'h', 'i', 's', ' ', 's', 'e', 'n', 't', 'e', 'n', 'c', 'e'] myList.remove("X")

myList ['I', ' ', 's', 'h', 'a', 'l', 'l', ' ', 'd', 'e', 'l', 'e', 't', 'e', ' ', ' ', 'f', 'r', 'o', 'm', ' ', 't', 'h', 'i', 's', ' ', 's', 'e', 'n', 't', 'e', 'n', 'c', 'e']

myNewString = str(myList)

myNewString "['I', ' ', 's', 'h', 'a', 'l', 'l', ' ', 'd', 'e', 'l', 'e', 't', 'e', ' ', ' ', 'f', 'r', 'o', 'm', ' ', 't', 'h', 'i', 's', ' ', 's', 'e', 'n', 't', 'e', 'n', 'c', 'e']"

Grigorij Schleifer
Grigorij Schleifer
10,365 Points 
Python 2.7.10 (default, Oct 23 2015, 19:19:21) 
[GCC 4.2.1 Compatible Apple LLVM 7.0.0 (clang-700.0.59.5)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> myString = 'I shall delete X from this sentence'
>>> myString    
'I shall delete X from this sentence'
>>> myList = list(myString)
>>> myList
['I', ' ', 's', 'h', 'a', 'l', 'l', ' ', 'd', 'e', 'l', 'e', 't', 'e', ' ', 'X', ' ', 'f', 'r', 'o', 'm', ' ', 't', 'h', 'i', 's', ' ', 's', 'e', 'n', 't', 'e', 'n', 'c', 'e']
>>> myList.remove("X")
>>> myList
['I', ' ', 's', 'h', 'a', 'l', 'l', ' ', 'd', 'e', 'l', 'e', 't', 'e', ' ', ' ', 'f', 'r', 'o', 'm', ' ', 't', 'h', 'i', 's', ' ', 's', 'e', 'n', 't', 'e', 'n', 'c', 'e']
>>> "".join(myList)
'I shall delete  from this sentence'
>>>

1 Answer

Grigorij Schleifer
Grigorij Schleifer
10,365 Points

HI Robert,

you can use the join() method.

" ".join(myList)

Grigorij

Grigorij Schleifer
Grigorij Schleifer
10,365 Points

Or you can create a for loop that adds every letter from list to a new String. But this approach is very inefficient and overcomplicated.

for letter in list:
    print(letter, end='')
Robert Meador
Robert Meador
1,844 Points

Thanks. This did the trick.

I see that it works, but I guess I still don't understand why. So.... by using " ".join(myList) we're basically telling Python to join the list back into a string and to remove the whitespace between each character?

Grigorij Schleifer
Grigorij Schleifer
10,365 Points

Hi Robert,

you are right. join takes an iterable thing as an argument. Usually it's a list.

join connects strings together with a separator. The separator is what you place right before the join.

You can choose a separator. Like '&' or '%' or ' :) '

See the result:

>>> myString = 'I shall delete X from this sentence'
>>> list = list(myString)
>>> list
['I', ' ', 's', 'h', 'a', 'l', 'l', ' ', 'd', 'e', 'l', 'e', 't', 'e', ' ', 'X', ' ', 'f', 'r', 'o', 'm', ' ', 't', 'h', 'i', 's', ' ', 's', 'e', 'n', 't', 'e', 'n', 'c', 'e']
>>> '&'.join(list)
'I& &s&h&a&l&l& &d&e&l&e&t&e& &X& &f&r&o&m& &t&h&i&s& &s&e&n&t&e&n&c&e'
>>> '%'.join(list)
'I% %s%h%a%l%l% %d%e%l%e%t%e% %X% %f%r%o%m% %t%h%i%s% %s%e%n%t%e%n%c%e'
>>> '   :)   '.join(list)
'I   :)       :)   s   :)   h   :)   a   :)   l   :)   l   :)       :)   d   :)   e   :)   l   :)   e   :)   t   :)   e   :)       :)   X   :)       :)   f   :)   r   :)   o   :)   m   :)       :)   t   :)   h   :)   i   :)   s   :)       :)   s   :)   e   :)   n   :)   t   :)   e   :)   n   :)   c   :)   e'
>>>

The last one is my favorite :)

G