How to Convert an Integer to a String in Python

The quickest way to convert an integer to a string in Python is the built-in str() function: str(42) gives you '42'. When the number goes inside a sentence, an f-string does the conversion for you:

zip_code = 30301
str(zip_code)          # '30301'
f"Zip: {zip_code}"     # 'Zip: 30301'

Nothing here needs a package; it’s plain Python 3.12.5, and I captured each run in a Windows Command Prompt.

Below you’ll find four ways to cast an int to a string, the TypeError they fix, leading zeros and commas, binary and hex, lists of numbers, and the 4,300-digit limit.

4 ways to convert an integer to a string in Python

str(), f-strings, str.format() and the old % operator all produce the same text. They differ in how much formatting you can add:

zip_code = 30301
population = 498715

a = str(zip_code)
b = f"{zip_code}"
c = "{}".format(zip_code)
d = "%d" % zip_code

print(a, b, c, d)
print(type(a), a == b == c == d)
print(f"Atlanta, GA {zip_code} has {population:,} people")

Output:

30301 30301 30301 30301
<class 'str'> True
Atlanta, GA 30301 has 498,715 people

I use str() when I need the string on its own and f-strings everywhere else. You’ll mostly see %d in older code.

Why do I get TypeError: can only concatenate str (not “int”) to str?

Python won’t glue a string and an int together with +; it doesn’t guess what you meant. Convert the number first, or let an f-string or print() handle it:

items = 3

try:
    print("You have " + items + " items in your cart")
except TypeError as err:
    print("TypeError:", err)

print("You have " + str(items) + " items in your cart")
print(f"You have {items} items in your cart")
print("You have", items, "items in your cart")    # print() converts for you

Output:

TypeError: can only concatenate str (not "int") to str
You have 3 items in your cart
You have 3 items in your cart
You have 3 items in your cart

There’s a whole guide on concatenating a string and an int if you want more options.

Formatting an int as a string: zeros, commas and dollars

Format specs after a colon in an f-string control padding, separators and signs. These are the ones I reach for most with order numbers and prices:

order_id = 42
amount = 1234567
cents = 129999                        # store money as whole cents

print(str(order_id).zfill(6))         # leading zeros
print(f"{order_id:06d}")              # same thing with a format spec
print(f"{amount:,}")                  # thousands separators
print(f"${cents / 100:,.2f}")         # cents to a dollar string
print(f"{order_id:>8}|")              # right-aligned in 8 spaces
print(f"{-7:+d} {7:+d}")              # always show the sign

Output:

000042
000042
1,234,567
$1,299.99
      42|
-7 +7

Keeping money as whole cents avoids float rounding surprises until you display it. More on that in formatting numbers with commas.

Converting an int to a binary, octal or hex string

bin(), oct() and hex() return strings with a prefix. A format spec gives the same digits without one, and int(text, base) converts back:

n = 255

print(bin(n), oct(n), hex(n))         # with 0b / 0o / 0x prefixes
print(f"{n:b} {n:o} {n:x} {n:X}")     # without prefixes
print(f"{n:08b}")                     # padded to 8 bits
print(format(n, "x"), int("ff", 16))  # and back to an int

Output:

0b11111111 0o377 0xff
11111111 377 ff FF
11111111
ff 255

Going the other direction is covered in converting a binary string to an int and converting a hex string to an integer.

How do you convert a list of integers to a string?

str.join() only accepts strings, so a list of ints raises a TypeError. Map str over the list first:

digits = [4, 1, 5, 9]

try:
    print("".join(digits))
except TypeError as err:
    print("TypeError:", err)

print("".join(map(str, digits)))
print(", ".join(str(d) for d in digits))
print(int("".join(map(str, digits))) + 1)
print(list(str(8675309)))             # an int's digits as strings

Output:

TypeError: sequence item 0: expected str instance, int found
4159
4, 1, 5, 9
4160
['8', '6', '7', '5', '3', '0', '9']

list(str(n)) is a quick way to get the digits of a number. For more on joining, see concatenating a list of strings.

The 4,300-digit limit on int to string conversion

Since Python 3.11, converting a huge int to a string raises a ValueError past 4,300 digits. It’s a guard against denial-of-service attacks, and you can raise it when you really need to:

import sys

big = 10 ** 5000
try:
    s = str(big)
except ValueError as err:
    print("ValueError:", err)

print("limit:", sys.get_int_max_str_digits())
sys.set_int_max_str_digits(10_000)
print(len(str(big)), "digits after raising the limit")

Output:

ValueError: Exceeds the limit (4300 digits) for integer string conversion; use sys.set_int_max_str_digits() to increase the limit
limit: 4300
5001 digits after raising the limit

You’ll only hit this with giant numbers, like factorials of big values. Everyday ints never come close.

Int to string in Python: which method to use

Goal	Use	Result
Plain conversion	str(n)	'1234'
Inside a sentence	f"Total: {n}"	'Total: 1234'
Commas	f"{n:,}"	'1,234'
Leading zeros	f"{n:06d}"	'001234'
Hex	f"{n:x}"	'4d2'

When you’re ready for more string conversions, try these:

• Convert a string to an integer in Python
• Concatenate a string and a float
• Format decimal places with f-strings
• Check the type of a variable in Python

Frequently asked questions