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pythonstringdecimal
Sankar A
Sankar A

Reputation: 779

How do I convert strings into decimal numbers?

I have a python list with strings in this format:

A1 = [' "29.0" ',' "65.2" ',' "75.2" ']

How do I convert those strings into decimal numbers to perform arithmetic operations on the list elements?

Upvotes: 77

Views: 295097

Answers (8)

Nids Barthwal
Nids Barthwal

Reputation: 2419

If you are converting price (in string) to decimal price then....

from decimal import Decimal

price = "14000.45"
price_in_decimal = Decimal(price)

Upvotes: 26

Ruhul Amin
Ruhul Amin

Reputation: 1

There are two floating-point data types. Float and Decimal. It depends on your program demand which one you want to use. Decimal provides a high level of accuracy and it's more precise than Float.

To convert a value string to float just do it:

num = "29.0"
print (float(num))

To convert string to decimal

from decimal import Decimal
num = "29.0"
print (Decimal(num))

For your specific question, you can use the below code. Both are working for me.

from decimal import Decimal
import re

result = [float(x.strip(' "')) for x in A1]
print(result)
#[29.0, 65.2, 75.2]


result = [Decimal(x.strip(' "')) for x in A1]
print(result)
#[Decimal('29.0'), Decimal('65.2'), Decimal('75.2')]


result = [float(re.search(r'\d+.\d+',number).group()) for number in A1]
print(result)
#[29.0, 65.2, 75.2]

result = [Decimal(re.search(r'\d+.\d+',number).group()) for number in A1]
print(result)
#[Decimal('29.0'), Decimal('65.2'), Decimal('75.2')]

Upvotes: 0

All Іѕ Vаиітy
All Іѕ Vаиітy

Reputation: 26492

In Python there are two floating point datatypes Float and Decimal. The use case depends on the precision of decimal you want in your program. Float is quick and Decimal is precise.

To convert a string to a floating point number just do

import decimal
float('1.2')
decimal.Decimal('1.2')

Analysing Float and Decimal objects

>>> import sys
>>> from decimal import Decimal

>>> num = '1.2'

>>> float(num)
1.2

>>> Decimal(num)
Decimal('1.2')


>>> # Precision
>>> float(1.2)
1.2

>>> Decimal(1.2)
Decimal('1.1999999999999999555910790149937383830547332763671875')


>>> # Memory usage
>>> sys.getsizeof(Decimal(num))
104

>>> sys.getsizeof(float(num))
24


>>> # Performance
>>> %timeit float(num)
140 ns ± 2.27 ns per loop (mean ± std. dev. of 7 runs, 10000000 loops each)

>>> %timeit Decimal(num)
192 ns ± 9.42 ns per loop (mean ± std. dev. of 7 runs, 1000000 loops each)

In your particular case you can use @Mark Byers solution.

Upvotes: 5

Veera Balla Deva
Veera Balla Deva

Reputation: 788

If you are converting string to float:

import re
A1 = [' "29.0" ',' "65.2" ',' "75.2" ']
float_values = [float(re.search(r'\d+.\d+',number).group()) for number in A1]
print(float_values)
>>> [29.0, 65.2, 75.2]

Upvotes: -1

Mark Byers
Mark Byers

Reputation: 839144

If you want the result as the nearest binary floating point number use float:

result = [float(x.strip(' "')) for x in A1]

If you want the result stored exactly use Decimal instead of float:

from decimal import Decimal
result = [Decimal(x.strip(' "')) for x in A1]

Upvotes: 109

tekknolagi
tekknolagi

Reputation: 11022

A2 = [float(x.strip('"')) for x in A1] works, @Jake , but there are unnecessary 0s

Upvotes: 1

farzad
farzad

Reputation: 8855

use the built in float() function in a list comprehension.

A2 = [float(v.replace('"','').strip()) for v in A1]

Upvotes: 2

Jake
Jake

Reputation: 13151

You will need to use strip() because of the extra bits in the strings.

A2 = [float(x.strip('"')) for x in A1]

Upvotes: 3

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