Python double from string

Parameter:
It takes only one parameter and returns the Decimal object. Here, the string represents the string value that has to be converted to decimal.

In this example, we will consider a string and convert it into a decimal value.

from decimal import Decimal # Consider a string strValue = '120.678' print(strValue) # Get the type of strValue print(type(strValue)) # Convert the string to decimal decimalValue = Decimal(strValue) # Get the type of converted print(type(decimalValue))

Firstly, the string – 120.678 belongs to the str class (string class). After converting into decimal, the class type is decimal.Decimal.

In this example, we will consider 5 strings in a list and convert them into decimals.

from decimal import Decimal # Consider strings in a list strings = ['120.678','890.678','4.58','7.908','345.78897666'] print(strings) # Convert the strings to decimal for i in strings: print(Decimal(i)) # Get the type of converted print(type(Decimal(i)))

Summary

In this article, we have seen how to convert a string to a float or double using float() and Decimal() methods. You have to import the Decimal() method from the decimal module. Otherwise, it will return a no module found error. Thanks.

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Convert String to Double in Python

In this blog, we will learn different methods to convert a string to a double in Python, including using built-in functions, libraries, and custom conversion functions.

Introduction:

Converting data from one type to another is a common task in programming. In Python, a popular and versatile programming language, one common conversion is from a string to a double. A double, also known as a floating-point number, is a numeric data type that allows for decimal values. Converting a string to a double in Python can be achieved using various methods, and in this blog, we will explore different approaches with programs and outputs.

Method 1: Using the float() Function

The float() function in Python is a built-in function that can be used to convert a string to a double. It takes a single argument, the string that needs to be converted, and returns a floating-point number. Here’s an example program:

# Program to convert a string to a double using the float() function # Input string str_num = "3.14159" # Converting string to double double_num = float(str_num) # Output print("String:", str_num) print("Double:", double_num) print("Type of double:", type(double_num)) 

Output:

String: 3.14159 Double: 3.14159 Type of double:

In the above program, we have used the float() function to convert the string «3.14159» to a double. The resulting double value is 3.14159, and its type is float, which is confirmed using the type() function. The float() function is a straightforward and commonly used method to convert a string to a double in Python.

Method 2: Using the ast.literal_eval() Function

The ast.literal_eval() function is another method in Python that can be used to convert a string to a double. It is part of the ast (Abstract Syntax Trees) module and can evaluate a string containing a literal Python expression, such as a numeric value. Here’s an example program:

# Program to convert a string to a double using the ast.literal_eval() function import ast # Input string str_num = "2.71828" # Converting string to double double_num = ast.literal_eval(str_num) # Output print("String:", str_num) print("Double:", double_num) print("Type of double:", type(double_num)) 

Output:

String: 2.71828 Double: 2.71828 Type of double:

In the above program, we have used the ast.literal_eval() function to convert the string «2.71828» to a double. The resulting double value is 2.71828, and its type is float, as confirmed using the type() function. The ast.literal_eval() function is useful when you want to evaluate a string containing a literal Python expression, including numeric values, and get the corresponding Python object.

Method 3: Using the numpy library

The numpy library is a popular numerical computing library in Python that provides many useful functions for working with numeric data. It also provides a convenient way to convert a string to a double using the numpy.float64() function. Here’s an example program:

# Program to convert a string to a double using the numpy library import numpy as np # Input string str_num = "1.61803" # Converting string to double double_num = np.float64(str_num) # Output print("String:", str_num) print("Double:", double_num) print("Type of double:", type(double_num)) 

Output:

String: 1.61803 Double: 1.61803 Type of double:

In the above program, we have used the numpy.float64() function from the numpy library to convert the string » 1.61803 » to a double. The resulting double value is 1.61803, and its type is numpy.float64 , which is a floating-point data type provided by numpy. The numpy library is widely used in scientific computing and data analysis tasks, making this method useful in such scenarios.

Method 4: Using Custom Conversion Functions

Another approach to convert a string to a double in Python is to define custom conversion functions. These functions can parse the string and extract the numerical value using string manipulation techniques, and then convert it to a double using built-in functions or mathematical operations. Here’s an example program:

# Program to convert a string to a double using custom conversion functions # Custom conversion function def string_to_double(str_num): # Parse the string and extract numerical value num_str = "" decimal_count = 0 for char in str_num: if char.isdigit() or char == '.': num_str += char if char == '.': decimal_count += 1 if decimal_count > 1: break else: break # Convert numerical value to double try: double_num = float(num_str) return double_num except ValueError: raise ValueError("Invalid string format") # Input string str_num = "123.45" # Converting string to double using custom function double_num = string_to_double(str_num) # Output print("String:", str_num) print("Double:", double_num) print("Type of double:", type(double_num)) 

Output:

String: 123.45 Double: 123.45 Type of double:

In the above program, we have defined a custom conversion function called string_to_double() that takes a string as input and parses it to extract the numerical value. The function iterates through each character in the input string and appends it to a new string num_str only if it is a digit or a decimal point. It also keeps track of the number of decimal points encountered to ensure that the string represents a valid double value. Then, the extracted numerical value is converted to a double using the float() function, and the resulting double value is returned. This method provides flexibility in handling different string formats and allows for customization as needed.

Conclusion:

Converting a string to a double in Python is a common task in many applications, and there are multiple methods available to achieve this. In this blog, we have explored four different approaches, including using the float() function, the ast.literal_eval() function, the numpy library, and custom conversion functions. We have provided example programs and outputs for each method to illustrate how they work.

The float() function is a straightforward and commonly used method, while the ast.literal_eval() function is useful when evaluating literal Python expressions. The numpy library provides a convenient way to work with numeric data, and custom conversion functions allow for flexibility and customization. Depending on the specific requirements of your application, you can choose the method that best fits your needs.

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