--- title: 2.8 Type Conversion description: "Sometimes a value needs to be converted from one data type to another. This process is called **type conversion**. For example: - Converting user input (string) into an integer. - Converting an integer into a floating-point number. - Converting a…" url: "https://edcret.in/docs/python-programming/basic-refreshers-python/2-8-type-conversion/" updated: "2026-07-29" category: Python Programming / Basic Refreshers --- # 2.8 Type Conversion Sometimes a value needs to be converted from one data type to another. This process is called **type conversion**. For example: - Converting user input (string) into an integer. - Converting an integer into a floating-point number. - Converting a number into a string for display. - Converting collections such as lists into tuples. Python provides several built-in functions to perform type conversion. Some commonly used conversion functions are: - `int()` - `float()` - `str()` - `bool()` - `list()` - `tuple()` - `set()` --- ## Example 1: Converting a String to an Integer **main.py** ``` number = "100" value = int(number) print(value) print(type(value)) ``` ### Output ``` 100 ``` ### Explanation - `number` stores the string `"100"`. - The `int()` function converts the string into an integer. - The converted value is stored in `value`. - The data type changes from `str` to `int`. --- ## Example 2: Converting an Integer to a Float **main.py** ``` number = 25 value = float(number) print(value) print(type(value)) ``` ### Output ``` 25.0 ``` ### Explanation - `number` is an integer. - The `float()` function converts it into a floating-point number. - The decimal part `.0` is automatically added. - The resulting data type is `float`. --- ## Example 3: Converting a Float to an Integer **main.py** ``` price = 99.95 value = int(price) print(value) ``` ### Output ``` 99 ``` ### Explanation - `price` stores a floating-point number. - `int()` removes the fractional part. - The value is **truncated**, not rounded. - Therefore, `99.95` becomes `99`. --- ## Example 4: Converting a Number to a String **main.py** ``` age = 25 text = str(age) print(text) print(type(text)) ``` ### Output ``` 25 ``` ### Explanation - `age` is an integer. - `str()` converts the integer into a string. - This is useful when combining numbers with text. --- ## Example 5: Converting User Input **main.py** ``` age = int(input("Enter your age: ")) print(age + 5) ``` ### Sample Input ``` Enter your age: 25 ``` ### Output ``` 30 ``` ### Explanation - `input()` returns a string. - `int()` converts the string into an integer. - The program can now perform arithmetic operations. --- ## Example 6: Converting to Boolean **main.py** ``` print(bool(1)) print(bool(0)) print(bool("Python")) print(bool("")) ``` ### Output ``` True False True False ``` ### Explanation - Non-zero numbers evaluate to `True`. - Zero evaluates to `False`. - Non-empty strings evaluate to `True`. - Empty strings evaluate to `False`. --- ## Example 7: Converting a List to a Tuple **main.py** ``` numbers = [10, 20, 30] data = tuple(numbers) print(data) print(type(data)) ``` ### Output ``` (10, 20, 30) ``` ### Explanation - `numbers` is a list. - `tuple()` converts the list into a tuple. - The data type changes from `list` to `tuple`. --- ## Example 8: Converting a Tuple to a List **main.py** ``` numbers = (10, 20, 30) data = list(numbers) print(data) print(type(data)) ``` ### Output ``` [10, 20, 30] ``` ### Explanation - `numbers` is a tuple. - `list()` converts the tuple into a list. - The resulting object is mutable. --- ## Example 9: Converting a List to a Set **main.py** ``` numbers = [10, 20, 20, 30, 30] data = set(numbers) print(data) ``` ### Output ``` {10, 20, 30} ``` ### Explanation - `set()` converts the list into a set. - Duplicate values are automatically removed. - Sets store only unique elements. --- ## Example 10: Multiple Type Conversions **main.py** ``` value = "25" number = int(value) decimal = float(number) text = str(decimal) print(number) print(decimal) print(text) ``` ### Output ``` 25 25.0 25.0 ``` ### Explanation - `"25"` is first converted into an integer. - The integer is converted into a floating-point number. - Finally, the floating-point number is converted into a string. - Python allows multiple conversions in sequence. --- # Common Mistakes ### 1. Converting an Invalid String to an Integer **Incorrect** ``` number = int("Hello") ``` ### Output ``` ValueError: invalid literal for int() with base 10: 'Hello' ``` **Reason** Only strings representing valid integers can be converted using `int()`. **Correct** ``` number = int("100") ``` --- ### 2. Assuming `int()` Rounds Values **Incorrect Assumption** ``` print(int(9.9)) ``` ### Incorrect Expectation ``` 10 ``` ### Actual Output ``` 9 ``` **Reason** `int()` truncates the decimal part instead of rounding. --- ### 3. Forgetting to Convert User Input **Incorrect** ``` age = input("Enter age: ") print(age + 5) ``` ### Output ``` TypeError: can only concatenate str (not "int") to str ``` **Reason** `input()` returns a string. **Correct** ``` age = int(input("Enter age: ")) print(age + 5) ``` --- ### 4. Assuming Every Value Can Be Converted **Incorrect** ``` value = float("Python") ``` ### Output ``` ValueError: could not convert string to float: 'Python' ``` **Reason** Only strings representing valid floating-point numbers can be converted using `float()`. --- # Best Practices - Convert values only when necessary. - Always validate user input before conversion in real-world applications. - Remember that `int()` truncates decimal values. - Use `str()` when combining numbers with text. - Be aware that some conversions may raise exceptions if the value is invalid. --- # Key Points to Remember - Type conversion changes a value from one data type to another. - Python provides built-in conversion functions such as `int()`, `float()`, `str()`, `bool()`, `list()`, `tuple()`, and `set()`. - `input()` returns a string, which often needs to be converted before performing arithmetic operations. - `int()` truncates the fractional part of floating-point numbers. - Invalid conversions raise exceptions such as `ValueError`. - Type conversion is widely used when processing user input and transforming data between different formats.