How to search a text file for lines that contain a specific word, then create a new file with the "found" lines

Question

I need to search some data (text file) for lines that contain a specific word, then create a new text file that only contains 'found' lines.

For example, if the data in the original text file (data.txt) was:

Child 9  60lbs  Female Diabetes
Adult 25 180lbs Male   ADHD
Adult 46 200lbs Female epilepsy
Child 10 65lbs  Female ADHD

And I was to search for the keyword 'Child', the new text file (output.txt) would be:

Child 9  60lbs  Female Diabetes
Child 10 65lbs  Female ADHD  

This is my code so far, I don't really know how to go about writing the found lines to a new file.

def main():
    
    Word1 = 'Child'
    
    #open an existing file. 
    OriginalData = open('recordData.txt', 'r')
    datalist = []

    for line in OriginalData.readlines():
            if Word1 in line: 
                #write the line to new file.
    
if __name__=="__main__":
    main()

Answer 1

search_word = 'your search word here'
with open('data.txt') as file:  # opens it, then closes it automatically at the end of the with block
    lines = [line for line in file.read().split('\n') if search_word in line]

with open('output.txt', 'w+') as output_file:  # 'w+' specifies it can be written to and created
    output_file.write('\n'.join(lines))

Now we can break down lines = [line for line in file.read().split('\n') if search_word in line]

file.read() returns a string of the whole file

.split('\n') turns the string into a list, breaking it at every newline ( '\n' is a newline)

if search_word in line so it only adds the lines with the words

'\n'.join(lines) puts the elected lines back together, then writes it to the file with write