CODEWITHSUNDEEP
python
anna
anna

Reputation: 121

how to extract a number from a line in a file where the number is connected to other charchter in python?

i am new to python and trying to write a simple code that reads lines from a given file, i am having a problem extracting a hexadecimal number from a line : for example i have the following file lines: 

# Program start at address 0, after reset.
I@0x00000000

D@0x000032A0

i want to extract the two hexadecimal numbers (they represent the start of instruction and data addresses) i wrote the following code and the method "get_start" is supposed to extract the first integer which is zero but instead i get the following output: ['0', '00000000']

my code :

import sys
import re

class Memory:
    def __init__(self):
        self.progStart=0
        self.data_start=0

    def get_start(self, line):
        patterns = [r'\d+']
        for p in patterns:
            match = re.findall(p, line)
            print(match)
            return match



    def sim_mem_reset(self, memFileName):
        with open(memFileName, 'r+') as fileName:
            for line in fileName:
                if line[0] == '#' or len(line.strip()) == 0:
                    continue
                if line[0] == 'I' and line[1] == '@':
                    self.progStart = self.get_start(line)   
                    print(self.progStart)
                if line[0] == 'D' and line[1] == '@':



# main
memory = Memory()
file_name = sys.argv[1]
print("Loading memory image file:", file_name)
memory.sim_mem_reset(file_name)

Upvotes: 0

Views: 45

Answers (2)

ForceBru
ForceBru

Reputation: 44828

You don't need regexes. It's very simple to solve using str.strip and the int class:

def get_start(self, line):
    '''
    Assumes `line` looks like: I@0x01234567
    '''
    return int(line.strip()[2:], 16)

Upvotes: 3

Jan Christoph Terasa
Jan Christoph Terasa

Reputation: 5935

The number is hexadecimal, and you can extract it by using str.split():

s = 'I@0x00000000'
num = int(s.split('@')[1], 16)

This will extract the hexadecimal number after the '@' character.

Upvotes: 1

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