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How to Convert an Int to a String in Python

By (LinkedIn) · Every code example is run and checked on Python 3.13 (how we test) · Last updated

Short answer
Use str(number), for example str(42) returns "42". For formatting such as padding or commas, use an f-string like f"{n:,}".

Numbers and text are different types in Python, so you cannot join them directly with +. To build a message, a file name or an ID, you first turn the integer into a string. Type casting with str() is the shortest route, and f-strings do the conversion for you while you format.

Which tool is best depends on whether you only need the digits or also want control over the look of the text.

Syntaxstr(number) or f"{number}"
ReturnsA new str
FailsNever for integers (any int can be converted)
Oppositeint(text)

Convert with str()

str() returns the decimal text of the number. The original integer is unchanged.

Python 
items = 3
message = "Items in cart: " + str(items)
print(message)
print(type(str(items)).__name__)





      
      
    

    

    
    

      
Convert with f-strings and format()

      
An f-string converts the value and lets you add a format specifier after a colon. This is usually the cleanest way to put numbers inside sentences.



  

    Python
    

      
      
      
      
    

  

  
n = 1234567
print(f"{n}")
print(f"{n:,}")
print(f"{7:03d}")
print(format(10, "b"))

  
  
  
  

    
      
      
    
    
  

  





      
      
    

    
    
    

      
Which method should you pick?

      
      
      
      

        
        
MethodExampleResultBest for

        
str()str(42)'42'Plain conversion
f-stringf"{42}"'42'Text with several values
Thousands separatorf"{1234567:,}"'1,234,567'Display to people
Zero paddingf"{7:03d}"'007'IDs, file names
Binary / hexformat(255, "x")'ff'Other bases

      

      
    

    
    
    

      
Why you cannot join a string and an int with +

      
"Total: " + 5 fails because Python will not guess how to mix types. Either convert with str(), use an f-string, or pass several arguments to print(), which converts for you. The error is a TypeError. To go the other way, see converting a string to an int.

      
      
    

    
    
    

      
Converting many integers at once

      
To turn a whole list of numbers into text, use map(str, numbers) or a comprehension, then join them into one string.

      
      
    

    
    

    
    

      
Examples you can run

      
Press Run, then edit the code and run it again.

      
      

        
Build a message from an integer

        
Both approaches produce the same text.

        

  

    Build a message from an integer
    

      
      
      
      
    

  

  
count = 5
print("Items: " + str(count))
print(f"Items: {count}")

  
  
  
  

    
      
      
    
    
  

  
Expected outputItems: 5
Items: 5




      

      
      

        
Format for display and file names

        
Commas for readability and zero padding for sortable names.

        

  

    Format for display and file names
    

      
      
      
      
    

  

  
revenue = 2500000
invoice = 42
print(f"Revenue: {revenue:,}")
print(f"invoice_{invoice:05d}.pdf")

  
  
  
  

    
      
      
    
    
  

  
Expected outputRevenue: 2,500,000
invoice_00042.pdf




      

      
      

        
Edge case: negative numbers, zero and digit access

        
The minus sign is part of the string. Converting also lets you work with individual digits.

        

  

    Edge case: negative numbers, zero and digit access
    

      
      
      
      
    

  

  
print(str(-15))
print(str(0))
n = 9047
digits = [int(d) for d in str(n)]
print(digits)
print(sum(digits))

  
  
  
  

    
      
      
    
    
  

  
Expected output-15
0
[9, 0, 4, 7]
20




      

      
    

    

    
    

      
Common mistakes

      
      

        
Concatenating text and a number

        

          
✗ Wrong
age = 30
print("Age: " + age)
TypeError: can only concatenate str (not "int") to str

          
✓ Right
age = 30
print("Age: " + str(age))

        

        
Convert the number first with str() or use an f-string.

      

      
      

        
Expecting str() to change the variable

        

          
✗ Wrong
n = 10
str(n)
print(n + 1)
11 (n is still an int, the converted string was thrown away)

          
✓ Right
n = 10
text = str(n)
print(text + "1")

        

        
Assign the result: n = str(n), or keep a separate variable.

      

      
      

        
Using len() on an integer

        

          
✗ Wrong
print(len(12345))
TypeError: object of type 'int' has no len()

          
✓ Right
print(len(str(12345)))

        

        
Convert to a string first, then count characters.

      

      
    

    

    
    

      
How to Convert an Int to a String in Python: questions people ask

      
How do I convert an int to a string in Python?
Use str(number), for example str(100) gives "100". An f-string such as f"{number}" does the same.
How do I convert an int to a string with leading zeros?
Use a format specifier: f"{7:03d}" gives "007", or str(7).zfill(3).
Is there a size limit when converting a huge int to str?
Yes, from Python 3.11 a decimal conversion of more than 4300 digits raises ValueError unless you raise the limit with sys.set_int_max_str_digits(). Normal numbers are never affected.

    

    

    
    

      
Keep learning

      
Step-by-step lessons:
Python CastingPython f-StringsPython Numbers

      
Related:
How to Convert a String to an Int in PythonHow to Convert a List to a String in PythonHow to Convert a Float to an Int in Python

      
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