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Learn to program with Python

Difference Between Strings and Numbers #

In Python, there is a fundamental difference between numbers and number strings. Numbers are a numeric data type that can be used in mathematical calculations, while number strings are simply strings of characters that happen to contain digits.

Let's take a look at some examples to see the difference in action.

# Examples of numbers
x = 5
y = 3.14
z = -10

# Examples of number strings
a = "123"
b = "-4.56"
c = "1.2e-3"

In this example, x, y, and z are all numeric variables. They can be used in mathematical calculations, such as addition, subtraction, multiplication, and division. For example:

result = x + y  # result is now 8.14

On the other hand, a, b, and c are all number strings. They are not numeric data types, so they cannot be used in mathematical calculations directly. If you try to perform mathematical operations on number and string, Python will raise a TypeError.

result = a + x # This will raise a TypeError
result_2 = a + b # This will give a new string "123-4.56" instead

Converting strings to numbers #

To perform mathematical operations on number strings, you first need to convert them to numeric data types using functions like int(), float(), or complex(). For example:

i = int(a)  # i is now the numeric value 123
j = float(b)  # j is now the numeric value -4.56
k = complex(c)  # k is now the complex value (1.2e-3+0j)

Converting other data types to strings #

You can convert other data types, such as numbers or booleans, to strings using the str() function. For example:

my_number = 42
my_string = str(my_number)
print(type(my_string)) # Output <class 'str'>

You can access individual characters in a string using indexing, and you can extract substrings using slicing. You can't do this with numbers, since they don't have individual "characters" to extract. For example:

my_string = "Hello, world!"
print(my_string[0])   # "H"
print(my_string[7:12])  # "world"

In general, it's important to keep in mind the difference between numbers and number strings in Python. Make sure to use the appropriate data type for the task at hand, and convert between data types as necessary.

Exercise #

  • Use the converting function int() or float() to change the value of string_number so that the result is equal to 40
  • Do not change the first two lines of code
Output will be displayed here