Read next line in Python

Question

I am trying to figure out how to search for a string in a text file, and if that string is found, output the next line.

I've looked at some similar questions on here but couldn't get anything from them to help me.

This is the program I have made. I have made it solely to solve this specific problem and so it's also probably not perfect in many other ways.

def searcher():
    print("Please enter the term you would like the definition for")
    find = input()
    with open ('glossaryterms.txt', 'r') as file:
        for line in file:
            if find in line:
                print(line)

So the text file will be made up of the term and then the definition below it.

For example:

Python
A programming language I am using

If the user searches for the term Python, the program should output the definition.

I have tried different combinations of print (line+1) etc. but no luck so far.

Answer 1

your code is handling each line as a term, in the code below f is an iterator so you can use next to move it to the next element:

with open('test.txt') as f:
    for line in f:
        nextLine = next(f)
        if 'A' == line.strip():
            print nextLine

Answer 2

If your filesize is small, then you may simply read the file by using readlines() which returns a list of strings each delimited by \n character, and then find the index of the selected word, and the print the item at position + 1 in the given list.

This can be done as:

def searcher():
    print("Please enter the term you would like the definition for")
    find = input()

    with open("glossaryterms.txt", "r") as f:       
        words = list(map(str.strip, f.readlines()))
        try: 
            print(words[words.index(find) + 1])
        except:
            print("Sorry the word is not found.")

Answer 3

You could try it Quick and dirty with a flag.

with open ('glossaryterms.txt', 'r') as file:
  for line in file:
    if found:
        print (line)
        found = False
    if find in line:
        found = True

It's just important to have the "if found:" before setting the flag. So if you found your search term next iteration/line will be printed.

Answer 4

In my mind, the easiest way would be to cache the last line. This means that on any iteration you would have the previous line, and you'd check on that - keeping the loop relatively similar

For example:

def searcher():
    last_line = ""
    print("Please enter the term you would like the definition for")
    find = input()
    with open ('glossaryterms.txt', 'r') as file:
        for line in file:
            if find in last_line:
                print(line)
            last_line = line