Do you know the method to “Convert String to Double in Python Language?” If you are a newcomer to the Python Language Course, you should need to understand the concept. Otherwise, you are going to face a lot of troubles in the beginning itself.
The Python programming language is different than any other language. To make it small & concise, there are many different unique features involved. One of the features is the absence of Data Types which are required to declare any variable in the program.
To fully understand Python’s data handling, check out our guide on Different Kinds of Python Data Types and how they impact variable storage and operations.
In the absence of the Data types, Python uses String as the default data type. From that background, this article is developed. In this article, we will know why we need to convert Strings to Double or other data types multiple times in Python!
TL;DR: Convert String To Double In Python
Aspect | Summary |
Why Conversion Is Needed? | Python treats all user inputs as strings, so arithmetic operations on them cause TypeError. Conversion is required for numeric calculations. |
Double In Python? | Python does not have a Double data type. So, it uses the float, which is equivalent to double precision. |
Method 1: Using Float() | It is the most common approach. It converts a numeric string into a floating-point number in a simple and fast way. |
Method 2: Using The Decimal Module | This method is used for high-precision calculations. To avoid rounding errors present in floating-point numbers, this method is very useful. |
Method 3: Using NumPy | To convert a string to a 64-bit precision float, this method is used. In ML, scientific computing, and NumPy workflows, this method is highly used. |
Why We Should Convert String To Double In Python?
In Python, when a programmer takes input using the built-in `input()` function, the input is captured as a string. This means that regardless of the value the user enters (whether it’s a number, text, or any other value), Python treats it as a sequence of characters, represented by a string.
As Python is a dynamically typed language it means data types of variables are not declared beforehand and Python will not know what the user will enter. Hence, it represents the input as a collection of characters.
Here’s a simple example to illustrate the type of user input.
Code to illustrate the type of user input:
# Taking user input
message = input("Please enter a message: ")
pincode = input("Please enter the recipient pincode: ")
# Displaying the captured input
print("Message:", message , " " , type(message))
print("Pincode:", pincode, " ", type(pincode))
Output:
From the output, we can see despite varied data types, both user input of the message and pin code is
received as a string. So, now we can understand that the input-taking process in Python is different than any normal language.
Now, if any novice takes Number Input & directly performs an arithmetic operation on it, it will certainly prompt an error message. In the end, the programmer wants to do an Arithmetic Operation with a string value. We can understand the process with one example.
p = input("Enter Number: ") # Taking user input
p = p + 10 # Trying To Add
print("Result:", p) # Printing Values
Output :
The output shows that the TypeError message is coming as we are going to add the String Value with one integer value. This is the case for Double as well. If you want to add the string values with the Double the same TypeError message comes.
This is the reason, we have to convert String Values to Double in Python.
How To Check A Valid String Before Conversion In Python?
Before converting a string to a float, you have to check whether the string is a valid string or not. As a beginner, we will advise you to do the practice. When you become an expert, it will not be a necessity.
To validate a string before converting it to a double, the Try-Except block will be used. Let us check it.
def check(value):
try:
float(value) # If Conversion Is Possible
return True
except ValueError: # If There Is Any Invalid String
return False
print("Conversion Possible For 12.34? ", check("12.34")) # Possible
print("Conversion Possible For 12.3.4? ", check("12.3.4")) # Not Possible
Explanation Of The Program:
- At first, in a function, a Try-Except block will be developed, which will check the conversion.
- We will try to convert a string to a float. If it is done, then True Boolean data will come.
- If the conversion is not possible, then False Boolean Data will come.
Output:
Comparison Table Between Try-Except Vs. Regex For Float Validation:
To validate the string for float() conversion, we have shown the Try-Except method. However, expect the Try-Except, the Regex Method is also considered an alternative to it.
Let us go through the following comparison table, where we will check the difference between these two for converting a string to a float.
Criteria | Try-Except For Float Validation | Regex For Float Validation |
Speed | Fast | Medium |
Strictness | Flexible | Strict |
Complexity | Low | High |
Read Ability | Clear | Dense |
Error Handling | Automatic | Manual |
What Are The Methods To Convert String to Double in Python? Read Below
Now, it is time to jump to the core concept of the article. Here, we are going to write down the functions that can be used to Change the String Function to Double without having any kind of issues. You can pick up any function mentioned below to do so.
Here, at first, we are going to use the Float function as it is the most important & highly used inbuilt function. After Float(), we are going to introduce two different functions as well.
Using float() Function
The most straightforward method is to use the built-in float() function, which converts a string to a
floating-point number. It represents numbers in base-2 format. float() has a fixed number of bits allocated for the mantissa (fractional part) and the exponent in the binary representation.
# _pi is currently a String
_pi = "3.14159265359"
value = float(_pi)
print(" Type of Pi" , value , " ", type(value))
Steps of the Program:
- At first, a normal string value is declared in the program with the decimal values as string.
- Now, we will use the Syntax float(variable-name).
- It will promptly convert the string data & store value in one variable.
- If we print the variable, we will find the Type is changed.
This will not only help you in overcoming challenges in understanding but also excel in your Python assignments.
Output:
From the above output, we can see that the Class has now changed. It is now pointing to the Float variable. The Float Variable is the smaller part of the Double. So, we can say the string is now converted to a Double value.
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Using Decimal Module
After the Float() Function, the Decimal function can be the next one. It is the function that works similarly to Float(). The Decimal Module provides precise decimal representation without rounding errors. It represents numbers in base-10 format.
from decimal import Decimal
value_str = "3.14159"
value = Decimal(value_str)
print(value, " " , type(value))
Steps of The Program:
- We have to first import the Decimal Function from the Decimal Library itself.
- Now, a string variable is stored in the program that will be used in the future.
- We will store the decimal value in the variable using the syntax decimal(variable-name).
- Now, we can print the Type to see that changes.
Output:
The above output clearly shows that the Class is now marked as the Decimal. As we are using the Decimal function, it is being changed to Decimal. In the previous one, it was the Float function as the Float is being used.
Using numpy Library:
NumPy library is mostly used when performing tasks on machine learning as it has more advanced
numerical functions. If you’re exploring Python for AI and ML, read our article on Reasons To Learn Python For Machine Learning to understand its growing role in data science. This can be another great alternative to change to Double from String in Python.
import numpy as np
golden_ratio = "1.61803398875"
phi = np.float64(golden_ratio)
print(phi, " ", type(phi))
Steps of the Program:
- We have to first call the Numpy in the program as NP to make it easy to use multiple times.
- Now, we will take a String Value with the decimal number in any variable.
- Using the syntax np.float64(Variable-Name), we will convert the value to the decimal.
- Now we will print the Type of the new variable.
Output:
From the above output, you can see that the Float64 is the new Type of the new variable. So, it is not the string number now. You can use the value for addition or any other arithmetic task. It will not provide any error.
Multiple Usage Of Float() Function While Converting String To Double:
Now, we are going to discuss some diverse illustrations on the Float() Method. The Float() Method is being used multiple times by more programmers than any other method, and it is really simple to use.
That is the reason we are diving a bit deep into the concept. Here, we will make the changes in the Float() function. And this will help us to play with the Precision values. So, let us check the following program.
import re
import locale
# Example 1: Convert A Positive Decimal String To Double
print("Example 1: ", float(+1.23))
# Example 2: Convert A Negative Integer String With Leading Whitespace To Double
print("Example 2: ", float('-99887\n'))
# Example 3: Convert A Special String To Double (Negative Infinity)
print("Example 3: ", float('-Infinity'))
# Example 4: Convert String With Comma Decimal To Double
value = "3,14"
value = value.replace(",", ".")
print("Example 4: ", float(value))
# Example 5: Remove Currency Symbol And Convert To Double
print("Example 5: ", float(re.sub(r'[^\d\.]', '', "$1,234.56")))
# Example 6: Convert Scientific Notation String To Double
print("Example 6: ", float(5.7E6))
# Example 7: Convert Locale-Aware String To Double
locale.setlocale(locale.LC_NUMERIC, 'de_DE.UTF-8')
print("Example 7: ", locale.atof("1.234,56"))
Explanation Of The Conversations:
- Positive Decimal String: If you want to convert a positive decimal string to a double, you can use the float() function, and without issues, it will be converted. Just the positive mark will be removed.
- Negative Integer String: Suppose you have given a negative integer string, then the negative mark will be present after the conversation as well. In the end, the decimal with zero will be added.
- Negative Infinity: If you are giving any special string like negative infinity to the program for conversion to a double, then such conversion will not be possible, and you will get the same data.
- String With Comma Decimal: In some regions, the comma is used as the decimal separator instead of the dot. As the comma will not go with the float(), we have to replace the comma with a dot.
- Currency Symbol: Sometimes, you will receive a string that includes the currency symbol as well. We will use the Regex and remove the currency symbol from there, and then convert.
- Scientific Notation String: You can also convert scientific decimal strings. You just have to give the scientific notation along with the ‘e’, and the rest, the float() function will calculate.
- Locale-Aware String: They are the special strings that have numeric values formatted by the rules of any specific country. Based on countries, the rules changed. So, we have to use the Locale Python Package to deal with it. Based on the country, the conversion will happen.
Output:
What Are Some Python Float Precision Limitations?
Now, from the above discussion, you have seen the conversion of strings to floats. However, there are some limitations of Python float precision that you have to remember while performing such actions.
Let us check the following list to know more about such limitations in floating-point precision.
- The Python Float uses Binary Base 2 representation, so some data might be inaccurate.
- If you are performing repetitive numerical operations, then accumulated errors can come in loops.
- The decimal values can’t be represented exactly, so rounding errors will occur.
- Due to binary floating-point conversion, operations like 0.1 + 0.2 will not give 0.3 as the result.
- You can see unexpected trailing digits while performing floating-point arithmetic.
What Are The Varied scenarios where you might need to convert a string to a double?
Now, before ending the topic, we are going to find out the scenarios where the Conversation from String to Double in Python Programming Language will become necessary. If you’re interested in working with indexed data while iterating, check out our guide on How To Use Enumerate In Python for a structured approach to looping.
We will discuss the fields where such conversation is highly needed.
We are going to make a list of domains where we have to convert String Data Type to Double for any kind of reason. Let us see each scenario one by one.
Data Parsing:
If you read data from external sources like Databases, you are going to get the data in the String format. Now, if you want to work on it, you have to make it to the Double or any Number format. Additionally, managing and retrieving elements from structured data is crucial—learn To Find Index In List Python to efficiently access stored values. In such cases, this conversation method can be used.
Mathematical Computation:
While performing a large Mathematical Computation, the Conversation method is being used. If there are any string values present in the process, they should be converted before going into the Mathematical computation. Additionally, if you’re dealing with numeric transformations, you might want to check out How To Square A Number In Python for more insights on handling mathematical operations in Python.
File I/O :
When parsing data from files, the data is often read as strings. If the file contains numeric values that you need to use for calculations, you would need to convert those strings to doubles before performing the calculations.
API Responses:
When working with APIs that provide data in string format, you might need to convert the string data to doubles to process it correctly.
Command-Line Arguments:
When a script or program accepts command-line arguments, these arguments are typically received as strings. If the arguments are supposed to be numeric values, you’d need to convert them to doubles.
Conclusion:
Converting strings to double (floating-point) values in Python is necessary when handling user inputs or working with numeric data. These techniques discussed differ based on specific use cases.
The primary method discussed involved a built-in `float()` function, which readily converts a string representation of a number to a floating-point value. However, for large floating numbers, it might give incorrect round-off values.
For situations very precision is important, the Decimal module comes in handy. Furthermore, NumPy offers more advanced features to work on floats and doubles. Additionally, understanding How To Delete A Variable In Python can help you manage memory efficiently and free up resources after computations.
Key Takeaways:
- The String to Double conversation is the basic need of the Python programming language.
- As every input data is stored as a String in Python, to make it calculable, it should be in Double.
- The Float() Function is the best function to convert into Double.
- There are many different ways the Float() Function can be used.
- Along with the Float(), there are Decimal & Numpy Functions present.
- From Mathematical Calculation to Data Parsing, the String should be converted.
