如何替换文本文件中每行空格前的第一个数字

Question

My file look like the following:

12.32 1:34 2:49 5:21 29:98
13.53 1:23 2:82 5:23 29:45
51.92 1:23 2:54 5:54 29:63
12.42 1:34 2:43 5:32 29:32

I am trying to replace every first number in each line by another number. So the output will be like

21.33 1:34 2:49 5:21 29:98
16.23 1:23 2:82 5:23 29:45
93.12 1:23 2:54 5:54 29:63
18.76 1:34 2:43 5:32 29:32 

What would be a good method?

I tried pointing to the number by

with open('file.txt', 'r') as file:
    line = file.readline()
    line[0]

but it just gives me first character, not the entire number. Thank you so much!

Answer 1

You can use following method to achieve this:-

data = None
with open('file.txt', 'r') as file:
    data = file.read()

def process_line_item(x):
    index = x[0]
    line_str = x[1]
    new_first_value = [str(x[0])] # you can put here new value depending on line index
    return ' '.join(new_first_value + x[1].split(' ')[1:])

new_data = '\n'.join(list(map(process_line_item, enumerate(data.split('\n')))))

with open('new_file.txt', 'w') as file:
    file.write(new_data)

file.txt

12.32 1:34 2:49 5:21 29:98
13.53 1:23 2:82 5:23 29:45
51.92 1:23 2:54 5:54 29:63
12.42 1:34 2:43 5:32 29:32

new_file.txt

0 1:34 2:49 5:21 29:98
1 1:23 2:82 5:23 29:45
2 1:23 2:54 5:54 29:63
3 1:34 2:43 5:32 29:32

Answer 2

you could use the csv module with delimiter=" " :

from csv import reader

with open('file.txt', 'r') as file:
    csv_reader = reader(file, delimiter=" ")
    for row in csv_reader:
        row[0] = '??.??'
        print(row)

which outputs

['??.??', '1:34', '2:49', '5:21', '29:98']
['??.??', '1:23', '2:82', '5:23', '29:45']
...

note that your numbers will be strings. you may have to convert them to floats:

floats = [float(item) for item in row]

if you then need to write the changes to a file you could similarly use a csv.writer .

Answer 3

This code should do the trick, however it may be a bit faulty and may need tweaking and testing a bit. I hope it helps though.

with open('file.txt', 'r') as file:
    file_content = file.read()
    list_content = [letter for letter in file_content]
    num_length = 0
    for i, char in enumerate(list_content):
        num_length += 1
        if list_content[i - 1] == '\n':
            num_length = 0

        elif char == ' ':
            start_index = i - num_length
            for _ in range(num_length + 1):
                list_content.pop(start_index)

            list_content.insert(start_index, your_new_number)

    out_text = ''.join(list_content)

with open('file.txt', 'w+') as file:
    file.write(out_text)