Converting string to integer and vice versa in Python

Question

I have a string for example

>>> sample = "Hello World!"

What I want to make a function which can convert sample to int. I know about chr() and ord(). I've used this so far:

For String to Int

>>> res="".join([str(ord(char)) for char in sample])
>>> print(res)
72101108108111328711111410810033

Now the problem arise. How can I convert res back to sample. Any suggestion would be appreciated.

Note: sample string can also have unicode characters in it

Edit :

nchars=len(sample)
res = sum(ord(sample[byte])<<8*(nchars-byte-1) for byte in range(nchars)) # string to int
print(''.join(chr((res>>8*(nchars-byte-1))&0xFF) for byte in range(nchars))) #int to string

I found this solution but this is very slow do someone know to improve this

• Michael Butscher: This is not possible because of different lengths of numbers (number strings, to be precise) no one can tell which digit belongs to which number.
• Yash Makan: @MichaelButscher I have found a solution but it is very slow. Can you tell me to better the solution in Edit
• Sayandip Dutta: How do you use bit shift operator on string in your solution?
• mhhabib: Combining all the ASCII together making a big string. You know ASCII values have different sizes like 0~255 so how can you sure what character you need? avoid combining all the ASCII together rather use an ASCII list then convert to string. Also your edited question isn't a valid way to get back
• Yash Makan: @SayandipDutta by converting string to byte

Answer 1

I am saving the num seperated by " " so it is possible to go back through convert it easier

This works and is simple:

i = "Hello World"
num = ""
for char in i:
 num += str(ord(char))+" "
print(''.join(num.split()))
back = ""
for n in num.split():
 back += chr(int(n))
print(back)

output:

721011081081113287111114108100
Hello World

Answer 2

sample = "Hello World!"
d1={k:str(ord(v)) for k,v in list(enumerate(sample))}
''.join(d1.values())
'72101108108111328711111410810033'
res1="".join([chr(int(char)) for char in d1.values()])
res1
'Hello World!'

In order to avoid the problem of which ord(chr) belongs to which chr? we need a mapping like data structure and dict is the best to store the each string and assign them to unique key using enumerate which will generate the keys on fly.

Our d1 looks like this:

{0: '72',
 1: '101',
 2: '108',
 3: '108',
 4: '111',
 5: '32',
 6: '87',
 7: '111',
 8: '114',
 9: '108',
 10: '100',
 11: '33'}

then comes the easy part converting the string values to int and applying chr on it to convert back into string.

Since OP donot want to use multiple variables or data structures.

sample = "Hello World!"
l_n=[str(ord(i))+str(ord('@')) for i in list(sample)]
text="".join(l_n)
n_l=[chr(int(i)) for i in text.split('64') if i.isnumeric()]
''.join(n_l)

The problem is we need to know where to apply char so I've added an extra @ to each letter so that it would be easy to convert it back

• Amit Verma: While this code may provide a solution to the question, it's better to add context as to why/how it works. This can help future users learn and eventually apply that knowledge to their own code. You are also likely to have positive-feedback/upvotes from users, when the code is explained.
• Yash Makan: @Ajay Thanks for your answer but I here I have to store d1 dictionary with the data of the number. You can think like I have to convert string to int in one pc and int to string in another pc. I have to store a limited amount of data. Can you suggest me any other way. Thanks
• Ajay: @YashMakan once d1 is generated this is not required on other PC
• Yash Makan: @Ajay consider line res1="".join([chr(int(char)) for char in d1.values()]). You have used d1 to convert int back to string. Therefore I have to store d1 and int in this case...