Convert Strings to Numbers and Numbers to Strings in Python

Converting strings to numbers and numbers to strings is a common task in Python. In this article, we’ll explore simple ways to convert between strings and numbers .

Using int() and str()

int() and str() functions in Python are commonly used for converting data types. The int() function changes a string or number into an integer, while the str() function converts a number or object into a string, making it easy to work with different data formats.

# Convert `s1` to integer
s1 = "123"
res = int(s1)
print(type(res))

# Convert `a` to string
a = 123
res= str(a)
print(type(res))

<class 'int'>
<class 'str'>

Let's understand different method to convert string to number and number to string.

Using eval()

eval() function evaluates a string as a Python expression and returns the result. While it can be used to convert strings to numbers, such as integers or floats .

# Convert `s1` to Integer
s1 = "123"
res = int(s1)
print(type(res))

# Convert `s2` to Float
s2 = "123.45"
res = float(s2)
print(type(res))

<class 'int'>
<class 'float'>

Using ast.literal_eval()

ast.literal_eval() function safely evaluates a string containing a Python literal or container display, such as strings, numbers, tuples, lists, dicts, sets, booleans, and None.

import ast 

# String to Integer
s1 = "123"
res = ast.literal_eval(s1)
print(type(res))

# String to Float
s2 = "123.45"
res = ast.literal_eval(s2)
print(type(res))

<class 'int'>
<class 'float'>

Explanation:

• ast.literal_eval(s1):This takes the string "123" and treats it as a Python number. Since "123" is a valid integer, it returns the integer 123.
• ast.literal_eval(s2):This takes the string "123.45" and treats it as a valid float, safely returning the value 123.45.

Using format()

format()is a efficient way to format strings, especially when we need to include numbers within the string or apply specific formatting like decimal precision or comma separators.

# Convert int to String
a = 123
res = "{}".format(a)
print(type(res))

# Convert float to String
b = 123.45
res = "{:.2f}".format(b)
print(type(res))

<class 'str'>
<class 'str'>

Explanation:

• "{}".format(a): This is used to format and insert the value of a (123) into the string placeholder {}. This converts the integer to its string representation, "123".
• "{:.2f}" : This ensures that the float is displayed with exactly two decimal places, even if the original value has more or fewer decimal places.

Using f-strings

F-strings is easy way to turn numbers (like integers and floats) into strings in Python. We can easily format numbers, such as displaying a specific number of decimal places or embedding numbers directly in the text.

# Integer to String
a = 123
res = f"{a}"
print(type(res))

# Float to String
b = 123.45
res = f"{b:.2f}"
print(type(res))

<class 'str'>
<class 'str'>

Explanation:

• f"{a}": This simply converts the integer to a string.
• f"{b:.2f}": This converts the float to a string, ensuring it always has 2 decimal places, even if the number has fewer.