Python Forum

Could anyone please help me for this question. I am trying to write a program that removes all spaces and tabs from a string that the user gives but I don't want to use any built in functions like replace() e.t.c. Only using while loops, and program outputs the exact string but all spaces and tabs removed.

An example output is:
Input: hi this is a test

Output: hithisisatest

What have you tried? Post your code in python tags, full traceback in error tags. Ask specific questions - we are glad to help, but we are not going to write your homework.

Also, don't post multiple times the same question and/or hijack threads. I've deleted your post in other user's thread.

Thank you for the reply, here is the code that I have. I'm trying to make it so that it checks if there are spaces in a loop and if there are, it removes the space.

newstring =""

string = input("Enter a string: ")

pos = 0

 

length = len(string)

while (pos<len(string)):

 

    if (string[1].isspace()!=True):

            pos = pos + 1

            newstring = newstring + string[pos]

            

            print(newstring)

           

            break

You are updating pos a little too early. When you add one to pos outside of the if statement then your code works as expected.

newstring =""
string = input("Enter a string: ")
pos = 0
length = len(string)
while (pos<length):
	if (string[pos].isspace()!=True):
		newstring = newstring + string[pos]
	pos += 1
print(newstring)

This helped, thanks so much.

This is generally frowned upon as a way to iterate.

pos = 0
length = len(string)
while (pos<len(string)):

Do you want length? Do you care about pos? No, these are only used being used to get what you really want, the characters from string. Instead of using a while loop with an index and a length you can get the characters directly using the iterator that is built into str.

for char in string:
    if (char.isspace()!=True):

This is generally frowned upon as a way to test:

if (char.isspace()!=True)

You wouldn't think of doing this:

if (a + b == 2) is True:

So why is it ok to do so with a function that returns True or False?

True and False should rarely be used, and should almost never appear in a comparison. char.isspace() returns True or False which are the type of things you need for an if statement. There is no need to use != True go get a logic value. If char.isspace() returns the wrong value for you program logic use "not" to invert the value.

for char in string:
    if (not char.isspace()):

Use of extra parenthesis is frowned upon. Python is not C and does not require parentheses surrounding the expression in an if statement.

for char in string:
    if not char.isspace():

Building up strings 1 character at a time is not considered a best practice.

newstring = newstring + string[pos]

Each time you execute this statement Python makes a brand new string and deletes the old string. The code works, but it requires a lot of work to work. If you had to do this kind of thing a lot or for a very large string it would be slow.

The way this kind of thing is typically done in Python is to collect all the characters in a list, then use str.join() to put all the characters back together.

string = input("Enter a string: ")
newstring = []
for char in string:
    if not char.isspace():
        newstring.append(char)
    newstring = ''.join(newstring)
print(newstring)

Unlike strings, lists are mutable in Python. Appending to a list does not require creating a new list and deleting the old list. Lists are also very efficient in Python. They have to be because lists and dictionaries are used everywhere.

And finally, using a loop is somewhat frowned upon when the logic can be cleanly encapsulated in a comprehension.

string = input("Enter a string: ")
newstring = ''.join([char for char in string if not char.isspace()])
print(newstring)

Comprehensions have some performance gain over using a for loop. A comprehension also makes it very clear that the result you want is a list (or a dictionary. There are dictionary comprehensions too). A Python coder will see the comprehension and know immediately that the purpose of the code is to make a list. This is clearer than having to read the code in a for loop. Note that "immediately" and "clearer" only apply for a simple comprehension with few loops and filters. A comprehension that is hundreds of characters long is not immediately clear and should be expanded out to regular for loops.

And I want to add that string is module from Standard Library, so don't use it as name.

Hello, this is actually a follow-up question on my code. So I actually forgot to put my code inside of a function at the start, so I added it in and its saying that its not giving the same output I had before.

string = input("Enter a string: \n")

 

def trim(string):

    newstring = ""

    pos = 0 

    length = len(string)

    

    while (pos < length

       ): 

       if (string[pos].isspace() != True

        ):

        newstring = newstring + string[

            pos] 

    pos += 1 

 

  

 

print(trim(""))

Please help below code.. output is Mone:

string = input("Enter a string: \n")
def trim(string):
newstring = ""
pos = 0
length = len(string)
while (pos < length
):
if (string[pos].isspace() != True
):
newstring = newstring + string[
pos]
pos += 1
print(trim(""))

I think you need to read up about Python functions. What did you expect to print. I expected "None" for the code you posted. At least I think that is what I expect since I cannot read your code without indentation. Please use proper tags to wrap your code as requested by buran after you initial post.