freeCodeCamp/guide/english/python/converting-integer-to-string-in-python/index.md

title
Converting Integer to String in Python

Converting Integer to String in Python

Unlike many other languages out there, Python does not implicitly typecast integers (or floats) to strings when concatenating with strings. Fortunately, Python has a handy built-in function str() which will convert the argument passed in to a string format.

The Wrong Way

Programmers coming from other languages may attempt to do the following string concatenation which produces an error:

age = 18

string = "Hello, I am " + age + " years old"

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The error that shows up is

Traceback (most recent call last):
  File "python", line 3, in <module>
TypeError: must be str, not int

TypeError: must be str, not int indicates that the integer must first be converted to a string to be concatenated.

The Correct Way

Simple concatenation example:

age = 18

print("Hello, I am " + str(age) + " years old")

# Output
# Hello, I am 18 years old

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Print 1 2 3 4 5 6 7 8 9 10 using a single string

result = ""

for i in range(1, 11):
    result += str(i) + " "

print(result)

# Output
# 1 2 3 4 5 6 7 8 9 10

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Line by Line explanation of the above code

1. First, a variable 'result' is assigned to an empty string.
2. For loop is being used to iterate over a list of numbers.
3. This list of numbers is generated using the range function.
4. So range(1,11) is going to generate a list of numbers from 1 to 10.
5. On each for loop iteration, the 'i' variable is going to take up values from 1 to 10.
6. On first iteration when the variable i=1, then the variable [result=result+str(i)+"(space character)"],str(i) converts the 'i' which is an integer value to a string value.
7. Since i=1, on the first iteration finally result=1.
8. And the same process goes on until i=10 and finally after the last iteration result=1 2 3 4 5 6 7 8 9 10.
9. Therefore when we finally print the result after the for loop the output on the console is '1 2 3 4 5 6 7 8 9 10'.

More Information:

Official Python documentation for str()