如何使用 python 仅搜索分隔文本文件的第一列

Question

Search through the first column of a piped '|'delimited.txt file containing 10 million rows using python. The first column contains phone number. I would like to output the entire row for that phone number

The file is 5GB.txt file, I am unable to open it in either ms excel or ms access. So i want to write a python code that can search through the file and print out the entire row which matches a particular phone number. Phone number is in the first column. I wrote a code but it searches the entire file and is very slow. I just want to search the first column and my search item is the phone number.

f = open("F:/.../master.txt","rt")      # open file master.txt
for line in f:                      # check each line in the file handle f
 if '999995555' in line:           # if a particular phone number is found
   print(line)                   # print the entire row
f.close()                            # close file

I expect the entire row to be printed on screen where the first column contains the phone number i am searching. but it is taking a lot of time as I am unable to search for the column as I don t know the code.

Answer 1

Well you are on the correct track there. Since it is a 5GB file, you probably want to avoid allocating 5GB of RAM for this. You probably better of using .readline() , since it is design for exactly your scenario (a big file).

Something like the following should do the trick, note that .readline() will return '' for the end of the file and '\n' for empty lines. The .strip() call is merely to remove the '\n' that .readline() returns at the end of each line actually in the file.

def search_file_line_prefix(path, search_prefix):
    with open(path, 'r') as file_handle:
        while (True):
            line = file_handle.readline()
            if line == '':
                break
            if line.startswith(search_prefix):
                yield line.strip()

for result in search_file_line_prefix('file_path', 'phone number'):
    print(result)