How to end for loop in Python?

Question

I'm new to programming and am playing around with Python scripting.

I'm trying to write a Python script that will read a text file and print to screen, search for a word, and every time it finds the word, to split the data of that line.

The test.txt file looks something like:

ape bear cat dog ape elephant frog giraffe ape horse iguana jaguar

I want the end result on screen to look like:

ape bear cat dog
ape elephant frog giraffe
ape horse iguana jaguar

My code so far:

file = "test.txt"
read_file = open(file, "r")
with read_file as data:
    read_file.read()
    print(data)
    word = "ape"
    for word in data:
        data.split()
        print(data)

I made the file a variable because I intend to use it many different times in the script.

When I tested the code, the for loop didn't stop after one loop. It eventually ended, but I'm sure if it was the code or program automatically ends infinite loops.

How do I edit the code so that the for loop will stop once it reaches the end of the file? And is there a more correct way to write this code?

Again, this is just an example file, not my actual file. Thanks!

Answer 1

>>> f = open("test.txt")
>>> a = f.read()
>>> f.close()
>>> a = a.replace("ape", "\nape")
>>> print(a)

ape bear cat dog
ape elephant frog giraffe
ape horse iguana jaguar

Answer 2

fileName = "test.txt"
read_file = open(fileName, "r")
with read_file as open_file:
    data = open_file.read().rstrip()
    keyword = "ape"
    data = ' '.join(["\n"*(word == keyword) + word for word in data.split()]).strip()
#   data = data.replace(keyword, "\n"+keyword).strip()
    print(data)

OUTPUT:

# ape bear cat dog 
# ape elephant frog giraffe 
# ape horse iguana jaguar

Answer 3

Try this, it does exactly what you intend:

file = "test.txt"
word = 'ape'
read_file = open(file, "r")
with read_file as data:
    for line in data:
        sp = line.split(word)
        for s in sp:
            if s:
                print(word + s)

Answer 4

The test.txt file looks something like:

ape bear cat dog ape elephant frog giraffe ape horse iguana jaguar

I want the end result on screen to look like:

ape bear cat dog
ape elephant frog giraffe
ape horse iguana jaguar

So you want every occurrence of 'ape' to be at the start of a line.

My code so far:

file = "test.txt"
read_file = open(file, "r")
with read_file as data:

There is no point in splitting these two up. If with is done with the file, it is closed and has to be open()ed again.

So just do

with open(file, "r") as data:

BTW, in your code, read_file and data are the same.

    read_file.read()

So you read the whole file into memory and discard the result.

    print(data)

Print the file object.

    word = "ape"

Assigns...

    for word in data:

... and immediately discards it again.

        data.split()

Splits the data and discards the result.

        print(data)

Prints the file object again.

But, as you have read the whole file, the for loop probably didn't run at all.

Improvements:

filename = "test.txt" # file is a builtin function
hotword = "ape"
with open(filename, "r") as read_file:
    for line in read_file:
        parts = line.split(hotword)
        if not parts[0]: # starts with the hotword, so 1st part is empty
            del parts[0]
        print ("\n" + ape).join(parts)

I made the file a variable because I intend to use it many different times in the script.

For the name it is ok, but the open file cannot be recycled, as with closes it.

When I tested the code, the for loop didn't stop after one loop.

Sure? What did it print?

Answer 5

Assuming that you're trying to learn about control flow and are not trying anything fancy with regular expressions or replacing the contents...

It looks like you are trying to do something like this (comments inline):

filename = 'test.txt'               # `file` is a Python built-in
with open(filename, 'r') as data:   # Open the file and close it when we're done
    for line in data:               # This will read one line at a time and exit the loop at EOF
        for word in line.strip().split():  # Strip off the newline and split the line into words
            if word == 'ape':       # If we've found our keyword
                print               #     Then Print a newline
            print word,             # Print every word, without a trailing newline

---

For Python 3, you'll need to change the syntax ever-so-slightly:

filename = 'test.txt'
with open(filename, 'r') as data:
    for line in data: 
        for word in line.strip().split():
            if word == 'ape':
                print()
            print(word, end=' ')

Answer 6

import re

file = "test.txt"
for line in open(file, 'r'):
    if(re.search('ape', line )):
        print(line)

Answer 7

You can use re.sub to escape the any word found not at the beginning of the line, and put a newline character before it, so you can use the following code.

Note that this looks for whole-words - eg, grape won't be matched with ape (unlike the str.replace solution offered):

import re

word = 'ape'
with open('yourfile') as fin:
    line = next(fin, '')
    print(re.sub(r'[^\b]({0}\s+)'.format(re.escape(word)), r'\n\1', line))