Python：替换每行文本文件中数组的索引元素

Question

I have a text file that looks similar to:

20, 32, 28, 32

27, 38, 30, 30

82, 39, 28, 18

29, 38, 10, 20

90, 28, 29, 09

If the value in the first column is > 50 then the remaining data is replaced with 0.

So it should look like this:

20, 32, 28, 32

27, 38, 30, 30

82, 0, 0, 0

29, 38, 10, 20

90, 0, 0, 0

I am really stuck on how to go about this. I have searched this site, but only find examples with one list eg a=[20,32,28,32] . but I have 5 different rows (is each row a separate list?)

Any help would her very much welcomed.

Answer 1

try this. COde need to be changed if number of columns changes

fle =open("C:\Python27\projects\infile.txt")
lst=fle.readlines()
lst=[i.strip() for i in lst]

for i in lst:
        j=i.split(',')
        if int(j[0]) > 50:

                for k in range(1,len(j)):
                    j[k]=0

        print ','.join(str(l) for l in j)
fle.close()

Answer 2

Just use for loop and do for each row what you'd do for one row.

Here's an example:

with open("example_file", "r") as f:
    for line in f.readlines():
        # do what you'd do with one line
        new_line = [int(l) for l in line.split(',')]
        if new_line[0] > 50:
            new_line[1:] = [0]*(len(new_line)-1)
        # process the line further ... save it to another file?

Answer 3

What you have found for a single list can also be used as multiple lists. Let's have a data.txt which contains out data like below:

data.txt

20, 32, 28, 32

27, 38, 30, 30

82, 39, 28, 18

29, 38, 10, 20

90, 28, 29, 09

Now we are going to read the data and process those as required. Finally we will write the processed data in a new file called output_data.txt . The program can be solved in the following way:

output_lines = []
with open("data.txt", "r") as input_file:
    input_lines = input_file.readlines()
    for line in input_lines:
        line = line.strip()
        if line!="":
            ar = list(map(int, line.split(",")))
            if ar[0] > 50:
                ar[1:] = [0] * (len(ar)-1)
            output_lines.append(", ".join([str(i) for i in ar]))
with open("output_data.txt", "w") as output_file:
    for line in output_lines:
        output_file.write(line+"\n")

output_data.txt contains:

20, 32, 28, 32
27, 38, 30, 30
82, 0, 0, 0
29, 38, 10, 20
90, 0, 0, 0

There are many alternatives to solve this. I have showed the most trivial one.