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Read in CSV file in Python differ from Uipath: Line-by-line loop needed?

I am new to Python. I used to use Uipath to read in CSV files and extract certain information using regex expression.
However, when I tried in Python I get error "NoneType object has no attribute 'group'", which mean a match is not found.
But my regex expression works fine in Uipath.
Python Code:
text_lines=f.readlines()
model_regex=re.compile(r'(?<=model choice :).*')
model=model_regex.search('text_lines')
print(model.group())
do I have to place my variable (text_line) in quotation marks here?
model=model_regex.search('text_lines')
I basically open a csv file and read it all the text using
text_lines=f.readlines()
But will text_lines look exactly like in the csv file? I noted when I use print(text_lines), all the lines look jumbled up.
Is there a way to read in text_lines to look exactly like in the csv files so that my regex expression work?
Or is it for Python , I need to loop line by line of the text_lines to look for the regex expression?
Thank you

Python pointers

I was asked to write a program to find string "error" from a file and print matched lines in python.
Will first open a file with read more
i use fh.readlines and store it in a variable
After this, will use for loop and iterate line by line. check for the string "error".print those lines if found.
I was asked to use pointers in python since assigning file content to a variable consumes time when logfile contains huge output.
I did research on python pointers. But not found anything useful.
Could anyone help me out writing the above code using pointers instead of storing the whole content in a variable.

There are no pointers in python, although something like pointer can be implemented, but is not worth the efforts for your case.
As pointed out in the solution of this link,
Read large text files in Python, line by line without loading it in to memory .
You can use something like:
with open("log.txt") as infile:
for line in infile:
if "error" in line:
print(line.strip()) .
The context managers will close the file automatically and it only reads one line at a time. When the next line is read, the previous one will be garbage collected unless you have stored a reference to it somewhere else.

You can use a dictionary by using key-pair value. Just dump the log file into dictionary wherein the key would be words and value would be the line number. So if you search for string "error" you will get the line numbers they are present it and accordingly you can print them. Since searching in dictionary or hashtable is in constant time O(1) it will take less time. But yes storing might take time depends if you avoid collision.

I used below code instead of putting the data in a variable and then for loop.
for line in open('c182573.log','r').readlines():
if ('Executing' in line):
print line
So there is no way that we can implement pointers or reference in python.
Thanks all

There are no pointers in python.
But something like pointer can be implemented, but for your case it's not required.
Try Below Code
with open('test.txt') as f:
content = f.readlines()
for i in content:
if "error" in i:
print(i.strip())
Even if you want to understand Python variables as pointers go to this link
http://scottlobdell.me/2013/08/understanding-python-variables-as-pointers/

Webbrowser() reading through a text file for URLS

I am trying to write a script to automate browsing to my most commonly visited websites. I have put the websites into a list and am trying to open it using the webbrowser() module in Python. My code looks like the following at the moment:
import webbrowser
f = open("URLs", "r")
list = f.readline()
for line in list:
webbrowser.open_new_tab(list)
This only reads the first line from my file "URLs" and opens it in the browser. Could any one please help me understand how I can achieve reading through the entire file and also opening the URLs in different tabs?
Also other options that can help me achieve the same.

You have two main problems.
The first problem you have is that you are using readline and not readlines. readline will give you the first line in the file, while readlines gives you a list of your file contents.
Take this file as an example:
# urls.txt
http://www.google.com
http://www.imdb.com
Also, get in to the habit of using a context manager, as this will close the file for you once you have finished reading from it. Right now, even though for what you are doing, there is no real danger, you are leaving your file open.
Here is the information from the documentation on files. There is a mention about best practices with handling files and using with.
The second problem in your code is that, when you are iterating over list (which you should not use as a variable name, since it shadows the builtin list), you are passing list in to your webrowser call. This is definitely not what you are trying to do. You want to pass your iterator.
So, taking all this in to mind, your final solution will be:
import webbrowser
with open("urls.txt") as f:
for url in f:
webbrowser.open_new_tab(url.strip())
Note the strip that is called in order to ensure that newline characters are removed.

You're not reading the file properly. You're only reading the first line. Also, assuming you were reading the file properly, you're still trying to open list, which is incorrect. You should be trying to open line.
This should work for you:
import webbrowser
with open('file name goes here') as f:
all_urls = f.read().split('\n')
for each_url in all_urls:
webbrowser.open_new_tab(each_url)
My answer is assuming that you have the URLs 1 per line in the text file. If they are separated by spaces, simply change the line to all_urls = f.read().split(' '). If they're separated in another way just change the line to split accordingly.

asking a person for a file to save in

What I'm trying to do is to ask a user for a name of a file to make and then save some stuff in this file.
My portion of the program looks like this:
if saving == 1:
ask=raw_input("Type the name file: ")
fileout=open(ask.csv,"w")
fileout.write(output)
I want the format to be .csv, I tried different options but can't seem to work.

The issue here is you need to pass open() a string. ask is a variable that contains a string, but we also want to append the other string ".csv" to it to make it a filename. In python + is the concatenation operator for strings, so ask+".csv" means the contents of ask, followed by .csv. What you currently have is looking for the csv attribute of the ask variable, which will throw an error.
with open(ask+".csv", "w") as file:
file.write(output)
You might also want to do a check first if the user has already typed the extension:
ask = ask if ask.endswith(".csv") else ask+".csv"
with open(ask, "w") as file:
file.write(output)
Note my use of the with statement when opening files. It's good practice as it's more readable and ensures the file is closed properly, even on exceptions.
I am also using the python ternary operator here to do a simple variable assignment based on a condition (setting ask to itself if it already ends in ".csv", otherwise concatenating it).
Also, this is presuming your output is already suitable for a CSV file, the extension alone won't make it CSV. When dealing with CSV data in general, you probably want to check out the csv module.

You need to use ask+'.csv' to concatenate the required extension on to the end of the user input.
However, simply naming the file with a .csv extension is not enough to make it a comma-separated file. You need to format the output. Use csvwriter to do that. The python documentation has some simple examples on how to do this.
I advise you not to attempt to generate the formatted comma-separated output yourself. That's a surprisingly hard task and utterly pointless in the presence of the built-in functionality.

Your variable ask is gonna be of type string after the raw_input.
So, if you want to append the extension .csv to it, you should do:
fileout = open(ask + ".csv", "w")
That should work.

String replacement on a whole text file in Python 3.x?

How can I replace a string with another string, within a given text file. Do I just loop through readline() and run the replacement while saving out to a new file? Or is there a better way?
I'm thinking that I could read the whole thing into memory, but I'm looking for a more elegant solution...
Thanks in advance

fileinput is the module from the Python standard library that supports "what looks like in-place updating of text files" as well as various other related tasks.
for line in fileinput.input(['thefile.txt'], inplace=True):
print(line.replace('old stuff', 'shiny new stuff'), end='')
This code is all you need for the specific task you mentioned -- it deals with all of the issues (writing to a different file, removing the old one when done and replacing it with the new one). You can also add a further parameter such as backup='.bk' to automatically preserve the old file as (in this case) thefile.txt.bk, as well as process multiple files, take the filenames to process from the commandline, etc, etc -- do read the docs, they're quite good (and so is the module I'm suggesting!-).

If the file can be read into memory at once, I'd say that
old = myfile.read()
new = old.replace("find this", "replace by this")
output.write(new)
is at least as readable as
for line in myfile:
output.write(line.replace("find this", "replace by this"))
and it might be a little faster, but in the end it probably doesn't really matter.