Subtracting 1 from the first number of a txt file using python-CodePudding

I have been stuck in this problem for hours now. I have a txt file where the following is the contents.

10 0.4600 0.4833 0.0433 0.0833
4 0.7833 0.6350 0.1167 0.0933
7 0.3583 0.4933 0.1667 0.1700

I'm trying to subtract 1 on the first numbers of the content to achieve the following result while maintaining the floating point numbers:

9 0.4600 0.4833 0.0433 0.0833
3 0.7833 0.6350 0.1167 0.0933
6 0.3583 0.4933 0.1667 0.1700

The following is my attempt to solve the problem but the whole content just disappears:

path = 'file.txt'
with open(path, "r ") as f:
  lines = f.readlines()
lines = str(int(lines[0].split()[0]) - 1)
with open(path, 'w') as file:
  file.writelines(lines)

I really need help for this problem. I've been trying for hours. Thanks in advance

CodePudding user response：

lines = list()

path = 'file.txt'
with open(path, "r ") as f:
    for line in f.readlines():
        split_line = line.strip("\n").split(" ")  # split on space character (and remove newline characters as well)
        lines.append(split_line)  # add split list into list of lines
  
  
for line in lines:
    line[0] = int(line[0]) - 1  # only subtract one from first element

with open(path, 'w') as file:  # rewrite to file

    for line in lines:
        # build the string to write
        write_me = ""
        for element in line:
            write_me  = f"{element} "
        file.write(write_me   "\n")

One thing to note is there will be trailing space and newline characters. If this is unwanted, let me know and I'll update this answer.

CodePudding user response：

your solution is no doubt a very accurate one. I just would like to make a few improvements:

lines = list()

path = 'file.txt'
with open(path, "r ") as f:
    for line in f.read().splitlines():
        # print(line)
        split_line = line.split(" ")  # split on space character (and remove newline characters as well)
        split_line[0] = str(
            int(split_line[0]) - 1)  # update the value inside the loop. the loop used in later not needed.
        lines.append(split_line)  # add split list into list of lines

# for line in lines:
#     line[0] = int(line[0]) - 1  # only subtract one from first element

with open(path, 'w') as file:  # rewrite to file
    for line in lines:
        # build the string to write
        # write_me = ""
        # for element in line:
        #     write_me  = f"{element} " # Another loop is not needed.
        write_me = ' '.join(line)  # Use join method to add the element together
        file.write(write_me   "\n")

Please compare yours code with mine and check the improvements.

Again, your code is absolutely correct just had a few scope of improvement. Please ignore my answer if you feel any other way.

Thanks!

CodePudding user response：

this would be cleaner in terms of lines of code:

import pandas as pd

f = 'G:\\path_to_file\\test.txt'
df = pd.read_csv(f, sep=" ", header=None)

df[0] = df[0]-1
print(df)

the result:

    0   1       2       3       4
0   9   0.4600  0.4833  0.0433  0.0833
1   3   0.7833  0.6350  0.1167  0.0933
2   6   0.3583  0.4933  0.1667  0.1700