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Python Type Casting

    Casting means changing a data type to another. It is popular in many programming languages like C/C++, Java, etc. Python also supports the type casting and it is done using casting functions. In python, there are two primary casting operations you can do and they are:

    1. Change string to other types such as Integer, Float, Boolean types.
    2. Convert other types to string

    Here are a list functions involved in casting from one type to another.

    Examples of Type Casting in Python

    The example contains following types.

    • Integer to string
    • Float to string
    • Boolean to string

    Integer to String

    num = 2233
result = str(num)
print(type(result))

    The output of the above code is

    ==== RESTART: C:/Python_projects/type casting/integer_to_string.py =======
<class 'str'>
>>>

    Float to String

    num_float = 344.55
result = str(num_float)
print(type(result))

    Once again the output is a string. Note that we are only checking the type and not printing the actual value.

    ===== RESTART: C:/Python_projects/type casting/float_to_string.py ========
<class 'str'>
>>>

    Boolean to String

    bool = True
result = str(bool)
print(type(result))

    Here is the output of the above code. Once again it is string, the value True will be "True". Note the double quotes around.

    ===== RESTART: C:/Python_projects/type casting/Bool_to_String.py =========
<class 'str'>
>>>

    Examples of String Type to Other Types

    In this section, we will convert other types to its string equivalent.

    • String to integer
    • String to float
    • String to Boolean

    String to Integer

    str = "Hello World"
str2 = "45"
result = int(str)
print(type(result))

    The output of the above program is given below. The str cannot be converted into an integer and produce following error.

    ==== RESTART: C:/Python_projects/type casting/String to Integer.py =======
Traceback (most recent call last):
  File "C:/Python_projects/type casting/String to Integer.py", line 3, in <module>
    result = int(str)
ValueError: invalid literal for int() with base 10: 'Hello World'
>>>

    However, the string “45” is converted to number 45 successfully. See the output below.

    ==== RESTART: C:/Python_projects/type casting/String to Integer.py =======
<class 'int'>
>>>

    String to Float

    Now we will check two cases , first we will

    1. convert a number string to float
    2. convert a float number string to float 
    number_string = "399"
result = float(number_string)
print(type(result))

    This was successful and the output is below.

    ======= RESTART: C:/Python_projects/Number_String_To_Float.py ===========
<class 'float'>
>>>

    Now we will convert a float string to float value.

    float_string = "3.14"
result = float(float_string)
print(result)
print(type(result))

    The output is given below.

    ======= RESTART: C:/Python_projects/Float_String_to_Float.py =========
3.14
<class 'float'>
>>>

    String to Boolean Value

    To convert a boolean string such as “True” or “False”, you have to use the ast or Abstract Syntax Trees.

    Visit following link to learn more about – ast

    It has many utilities function and one of them is ast.literal_aval() that evaluates string to other types such as Boolean.

    import ast
boolString = "True"
result = ast.literal_eval(boolString)
print(result)
print(type(result))

    The output is given below. Note that the result and its type both are printed.

    ======= RESTART: C:/Python_projects/bool_string_to_boolean.py ========
True
<class 'bool'>
>>>
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