value error string can not be converted to float?

Question

import scrapy
from scrapy import Field,Item
from itemloaders.processors import TakeFirst,MapCompose

def get_price(txt):

    value = txt.replace('1.359,20','1.359')
    value = txt.replace(',','.')
    value = txt.strip('1.499,00')
    value = txt.strip('R$')
    float(value)

class MultilaserItem(scrapy.Item):
# define the fields for your item here like:
# name = scrapy.Field()
title = Field(output_process=TakeFirst())
price = Field(input_processor=MapCompose(get_price),output_processor=TakeFirst())
#installment = Field(output_process=TakeFirst())

your text when i do this value = txt.replace(',','.')
should it not replace the value in 14,90 to 14.90? but i am stuck with error

ValueError: Error with input processor MapCompose: field='price' value=['R$ 14,90'] error='ValueError: Error in                MapCompose with <function get_price at 0x7fa825ee0b80> value=['R$ 14,90'] error='ValueError: could not convert string to float: ' 14,90

Asked By: frozen

||

Source

Answer 1

The posted code above only applies the last operation value = txt.strip('R$') that results with " 14,90" which is not a valid floating point number and raises a value error.

To perform multiple operations on a string then need to reassign the variable after each operation.

Try a function like the following to get the price from a string input:

def get_price(txt):
    txt = txt.replace(',','.')
    value = txt.strip('R$')
    return float(value)

price = get_price("R$ 14,90") 
print(f"{price:.2f}")

Output:

14.90

Answered By: CodeMonkey

Answer 2

value = txt.replace('1.359,20','1.359')
value = txt.replace(',','.')
value = txt.strip('1.499,00')
value = txt.strip('R$')

These replacements use the original value of txt, so they are not cumulative. Each one undoes the previous one. So you end up with only the final replacement of strip('R$'). The first three are discarded.

Answered By: John Gordon

value error string can not be converted to float?

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