Here is a snippet from a text file I am working on.
http://pastebin.com/4Uba5i4P
I would like to use python to detect those big repeating "~ Move" lines (Which are not identical except for the "~ Move" part.), and remove all but the first and last of those lines.
How I would I start to go about this?
You could read the file line by line like this:
`## Open the file with read only permit
f = open('myTextFile.txt')
## Read the first line
line = f.readline()
## If the file is not empty keep reading line one at a time #
# till the file is empty while line: print line
line = f.readline() f.close()`
With this you could then edit this sample to test each line using a regex like this:
`if line.find("~Move") == -1:
Break;
Else:
Line=Line [5:-1]`
Though this assumes that the ~Move is all at the beginning of the line. Hope this helps, if not leave a comment and I'll try and help.
Related
I am trying to delete a line from a text file after opening it and without storing it in any list variable using f.readlines() or anything like that.
I dont have an option to open the file and store the contents in a variable and make some changes and write them to another file or any kind of operations that would require to open the file and store them again in a list variable and make some changes and store them back to the file. The file is being constantly appended by some other program, so I cannot do any kind of that stuff.
I am using f.seek() to reset the pointer to the beginning of the file, and using f.readline() as well as f.tell() to know the length of the first line. After that I am trying to replace each character with a blank space using while loop.
pos=0
eol = 0
ll=0
with open('file1.txt','rb+') as f:
f.seek(pos,1) #position at the beginning of the file
print(f.readline()) #reading the first line
pos = f.tell() #storing the length of first line
#the while loop will run from 0 to pos and replace every character with blank space
while eol != pos:
with open('file1.txt','rb+') as f:
f.seek(eol,1)
f.write(b' ')
eol += 1 #incrementing the eol variable to move the file pointer to next character
the code is working fine but with one problem which I cant figure out what,
for example if this is the original file
file1.txt
this is line 1
this is line 2
this is line 3
after running the program , my output is
this is line 2
this is line 3
the first line is getting deleted but there is a bunch of white space in front of the 2nd line.
Maybe I am missing a simple logic here.
Any help will be appreciated.
Thank you
Update :
If i have understood it correctly I have changed the code and made it like this, and instead of b' ' i am putting '\r' as carraige return, which resulted in this :
the code :
while eol != pos-1:
with open('file1.txt','rb+') as f:
f.seek(eol,0)
f.write(b'\r')
eol += 1
the result :
original :
this is line 1
this is line 2
this is line 3
after execution
this is line 2
this is line 3
you see the 1st line is removed but followed with '\r'
Okay, I am building a little program that will help single out Nmap results:
#Python3.7.x
#
#
#
#report=input('Name of the file of Nmap Scan:\n')
#target_ip=input('Which target is the report needed on?:\n')
report = "ScanTest.txt"
target_ip = "10.10.100.1"
begins = "Nmap scan report for"
fhand = open(report,'r')
beginsend = "Network Distance:"
for num1,line in enumerate(fhand, 1):
line = line.rstrip()
if line.startswith(begins) and line.endswith(target_ip):
print(num1)
for num2,line in enumerate(fhand, 1):
line = line.rstrip()
if line.startswith(beginsend):
print(num2)
In my what im trying to do is get the first part of the scan results "target_ip" and with that i hope i can read the lines from there until there is a break in the line of the txt.
What this code does for me now is just get me the line number where i want to start.
In the second part of the code I tried getting the number of line for the last bit of text that i need. But it wont print. Im not sure if im going about this the right way or im not looking hard enough.
In short find my line and print until there is a break in the text.
The first loop exhausts all the lines in the file. When the second loop tries to run, there are no more lines to read and the loop exits immediately.
If you want the first loop to stop when it finds a matching line and allow the second loop to read the remaining lines, you can add a break statement in the if.
start_pattern = 'hello there'
end_pattern = 'goodblye now'
print_flag = False
with open('somefile.txt') as file:
for line in file:
if start_pattern in line:
print_flag = True
if print_flag:
print line
if end_pattern in line:
break
Ok so I have this code:
for line in fileinput.FileInput("zero.html",inplace=1):
if '{problem}' in line:
rep = 'a dynamic var'
line = line.replace('{problem}', rep)
print(line)
Now, the problem is that it replaces the text fine, but it deletes all other lines without '{problem}' in it. How can I replace '{problem}' with something else, without deleting the other lines? Also, I have multiple occurrences of '{problem}' in my file, and I want each one to be changed to a different, random string.
Thanks!
The if statement doesn't say what to do with the line if it doesn't contain '{problem}'. So as written, your code just ignores those lines. You could add an else clause that prints the line. Or you could just drop the if test, like this:
for line in fileinput.FileInput("zero.html", inplace=1):
rep = 'a dynamic var'
line = line.replace('{problem}', rep)
print(line)
The replace method will leave the line unchanged if it doesn't contain '{problem}'.
New to programming, looking for a deeper understanding on whats happening.
Goal: open a file and print the first 10 lines. (similar to head command)
Code:
with open('file') as f:
for i in range(0,10):
print([line.strip('\n') for line in f][i])
Result: prints first line fine, then returns the out of range error
File: Is a simple text file with 20 lines, no more than 50 chars per line
FYI - Removed range line and printed both type(list) and length(20). Printed specific indexes without issue (unless >1 in a row)
Able to get the desired result with different code, but trying to improve using with/as
You can actually iterate over a file. Which is what you should be doing here.
with open('file') as f:
for i, line in enumerate(file, start=1):
# Get out of the loop if we hit 10 lines
if i >= 10:
break
# Line already has a '\n' at the end
print(line, end='')
The reason that your code is failing is because of your list comprehension:
[line.strip('\n') for line in f]
The first time through your loop that consumes all of the lines in your file. Now your file has no more lines, so the next time through it creates a list of all the lines in your file and tries to get the [1]st element. But that doesn't exist because there are no lines at the end of your file.
If you wanted to keep your code mostly as-is you could do
lines = [line.rstrip('\n') for line in f]
for i in range(10):
print(lines[i])
But that's also silly, because you could just do
lines = f.readlines()
But that's also silly if you just want up to the 10th line, because you could do this:
with open('file') as f:
print('\n'.join(f.readlines()[:10]))
Some further explanation:
The shortest and worst way you could fix your code is by adding one line of code:
with open('file') as f:
for i in range(0,10):
f.seek(0) # Add this line
print([line.strip('\n') for line in f][i])
Now your code will work - but this is a horrible way to get your code to work. The reason that your code isn't working the way you expect in the first place is that files are consumable iterators. That means that when you read from them eventually you run out of things to read. Here's a simple example:
import io
file = io.StringIO('''
This is is a file
It has some lines
okay, only three.
'''.strip())
for line in file:
print(file.tell(), repr(line))
This outputs
18 'This is is a file\n'
36 'It has some lines\n'
53 'okay, only three.'
Now if you try to read from the file:
print(file.read())
You'll see that it doesn't output anything. That's because you've "consumed" the file. I mean obviously it's still on disk, but the iterator has reached the end of the file. But as shown, you can seek in the file.
print(file.tell())
file.seek(0)
print(file.tell())
print(file.read())
And you'll see your entire file printed. But what about those other positions?
file.seek(36)
print(file.read()) # => okay, only three.
As a side note, you can also specify how much to read:
file.seek(36)
print(file.read(4)) # => okay
print(file.tell()) # => 40
So when we read from a file or iterate over it we consume the iterator and get to the end of the file. Let's put your new tools to work and go back to your original code and explore what's happening.
with open('file') as f:
print(f.tell())
lines = [line.rstrip('\n') for line in f]
print(f.tell())
print(len([line for line in f]))
print(lines)
You'll see that you're at a different location in the file. And the second list comprehension produces an empty list. That's because when a list comprehension is evaluated it executes immediately. So when you do this:
for i in range(10):
print([line.strip('\n') for line in f][i])
What you're doing the first time, i = 0 and then the list comprehension reads to the end of the file. Now it takes the [0]th element of the list, or the first line in the file. But your file iterator is at the end of the file.
So now we get back to the beginning of the list and i = 1. Now we iterate to the end of the file, but we're already at the end so there are no lines to read, and we've got an empty list [] that we try to get the [0]th element of. But there's nothing there. So we get an IndexError.
List comprehensions can be useful, but when you're beginning it's usually much easier to write a for loop and then turn it into a list comprehension. So you might write something like this:
with open('file') as f:
for i, line in enumerate(file, start=10):
if i < 10:
print(line.rstrip())
Now, we shouldn't print inside a list comprehension, so instead we'll collect everything. We start out by putting what we want:
[line.rstrip()
Now add the for bit:
[line.rstrip() for i, line in enumerate(f)
And finally add the filter and our closing brace:
[line.rstrip() for i, line in enumerate(f) if i < 10]
For more on list comprehensions, this is a fantastic resource: http://treyhunner.com/2015/12/python-list-comprehensions-now-in-color/
First year Comp Sci student here.
I have an assignment that is asking us to make a simple game using Python, which takes an input file to create the game-world (2D grid). You're then supposed to give movement commands via user input afterwards. My program reads the input file one line at a time to create the world using:
def getFile():
try:
line = input()
except EOFError:
line = EOF
return line
...after which it creates a list to represent the line, with each member being a character in the line, and then creates a list containing each of these lists (amounting to a grid with row and column coordinates).
The thing is, I later need to take input in order to move the character, and I can't do this because it still wants to read the file input, and the last line from the file is an EOF character, causing an error. Specifically the "EOF when reading a line" error.
How can I get around this?
Sounds like you are reading the file directly from stdin -- something like:
python3 my_game.py < game_world.txt
Instead, you need to pass the file name as an argument to your program, that way stdin will still be connected to the console:
python3 my_game.py game_world.txt
and then get_file looks more like:
def getFile(file_name):
with open(file_name) as fh:
for line in fh:
return line
File interaction is python3 goes like this:
# the open keyword opens a file in read-only mode by default
f = open("path/to/file.txt")
# read all the lines in the file and return them in a list
lines = f.readlines()
#or iterate them at the same time
for line in f:
#now get each character from each line
for char_in_line in line:
#do something
#close file
f.close()
line terminator for the file is by default \n
If you want something else you pass it as a parameter to the open method (the newline parameter. Default=None='\n'):
open(file, mode='r', buffering=-1, encoding=None, errors=None, newline=None, closefd=True, opener=None)