Develop Reference

Python: Writing to file using while loop fails with no errors given

I am attempting to collect only certain type of data from one file. After that the data is to be saved to another file. The function for writing for some reason is not saving to the file. The code is below:
def reading(data):
file = open("model.txt", 'r')
while (True):
line = file.readline().rstrip("\n")
if (len(line) == 0):
break
elif (line.isdigit()):
print("Number '" + line + "' is present. Adding")
file.close()
return None
def writing(data):
file = open("results.txt", 'w')
while(True):
line = somelines
if line == "0":
file.close()
break
else:
file.write(line + '\n')
return None
file = "model.txt"
data = file
somelines = reading(data)
writing(data)
I trying several things, the one above produced a TypeError (unsupported operand). Changing to str(somelines) did solve the error, but still nothing was written. I am rather confused about this. Is it the wrong definition of the "line" in the writing function? Or something else?

See this line in your writing function:
file.write(line + '\n')
where you have
line = somelines
and outside the function you have
somelines = reading(data)
You made your reading function return None. You cannot concat None with any string, hence the error.

Assuming you want one reading function which scans the input file for digits, and one writing file which writes these digits to a file until the digit read is 0, this may help:
def reading(file_name):
with open(file_name, 'r') as file:
while True:
line = file.readline().rstrip("\n")
if len(line) == 0:
break
elif line.isdigit():
print("Number '" + line + "' is present. Adding")
yield line
def writing(results_file, input_file):
file = open(results_file, 'w')
digits = reading(input_file)
for digit in digits:
if digit == "0":
file.close()
return
else:
file.write(digit + '\n')
file.close()
writing("results.txt", "model.txt")

IndexError: list index out of range - PythonError

I'm creating a program that should create a file (.txt) based on each line of 'clouds.txt'. This is my code:
def CreateFile():
global file_name
f = open(file_name,"w+")
f.write(list_email + ":")
f.close()
def WriteInConfig():
f = open("config/config.txt","a")
f.write(list_name + "\n")
f.close()
with open("clouds.txt","r") as f:
list_lines = sum(1 for line in open('clouds.txt'))
lines = f.readline()
for line in lines:
first_line = f.readline().strip()
list_email = first_line.split('|')[1] #email
print("Email: " + list_email)
list_pass = first_line.split('|')[2] #pass
print("Pass: " + list_pass)
list_name = first_line.split('|')[3] #name
print(list_name)
global file_name
file_name = "config/." + list_name + ".txt"
with open('clouds.txt', 'r') as fin:
data = fin.read().splitlines(True)
with open('clouds.txt', 'w') as fout:
fout.writelines(data[1:])
CreateFile()
WriteInConfig()
The clouds.txt file looks like this:
>|clouds.n1c0+mega01#gmail.com|cwSHklDIybllCD1OD4M|Mega01|15|39.91|FdUkLiW0ThDeDkSlqRThMQ| |x
|clouds.n1c0+mega02#gmail.com|tNFVlux4ALC|Mega02|50|49.05|lq1cTyp13Bh9-hc6cZp1RQ|xxx|x
|clouds.n1c0+mega03#gmail.com|7fe4196A4CUT3V|Mega03|50|49.94|BzW7NOGmfhQ01cy9dAdlmg|xxx|xxx >
Everything works fine until 'Mega48'. There I get "IndexError: list index out of range"
>|clouds.n1c0+mega47#gmail.com|bd61t9zxcuC1Yx|Mega47|50|10|Xjff6C8mzEqpa3VcaalUuA|xxx|x
|clouds.n1c0+mega48#gmail.com|kBdnyB6i0PUyUb|Mega48|50|0|R6YfuGP2hvE-uds0ylbQtQ|xxx|x
|clouds.n1c0+mega49#gmail.com|OcAdgpS4tmSLTO|Mega49|50|28.65|xxx| >
I checked and there are no spaces/other characters. As you could see, after creating the file, the program deletes the line. After the error, if I'm starting the program again (and starts from 'Mega47') it doesn't show the error, and everything works as planned.
Any ideas how to fix this?

I see many mistakes in your code. First, what do you want with this list_lines = sum(1 for line in open('clouds.txt'))?
You have a problem in your for loop because you did lines = f.readline() so lines is the first line, then you do for line in lines where line will be each character of the first line and there are more character in the first line than lines in your file to read.
[edited]
you don't need to know the number of lines in the file to do a for loop. You can just do for line in f:, then you don't need to read the line again with readline it is already in the variable line

Python write blank

I'm trying to make a program which would replace tags in a markdown file (.md) as follow :
If it's an opening $ tag, replace it by \(, if it's a closing $ tag, replace it by \), copy every other characters.
Unfortunately, when I try it, the file written is really strange. Some lines are copied but others aren't. First, the first and last line of every of my test files weren't copied. Other lines in the middle weren't as well. Same text on different line are not both copied.
Here is my program :
import os
def conv1(path):
"""convert $$ tags to \( \)"""
file = open(path, mode ='r') # open lesson with $ (.md)
new = open(path + '.tmp', mode = 'w') # open blank file
test = 0
for lines in file:
line = file.readline()
i = 0
length = len(line)
while i < length:
if line[i] == '$':
if test % 2 == 0: # replace opening tag
line = line[:i] + '\(' + line [i + 1:]
elif test % 2 == 1: # replace closing tag
line = line[:i] + '\)' + line [i + 1:]
test +=1
i += 2
length += 1
else :
i += 1
new.write(line + '\n')
file.close()
new.close()
os.rename(str(path) + '.tmp', str(path))
print('Done!')
Do you have any idea how to fix my issue?
Thanks in advance
EloiLmr

These line are causing every other line to be skipped:
for lines in file:
line = file.readline()
Calling file.readline() unnecessarily advances the file pointer by one line. It's enough to iterate over the file:
for line in file:
...

Readline printing just characters

I run this code in the Python IDLE, and it will only return the amount of letters specified instead of the line specified.
if os.path.exists(saveDir + name + '.txt') == True:
print('welcome back ' + name + '.')
file = open(saveDir + name + '.txt')
race = file.readline(1)
else:
race = intro()
When I print the race variable, it comes out as the G (The input name is Grant).
The text file looks like this
Grant
Human
What Am I doing wrong?

race = file.readline(1) returns 1 byte (character) of the line (see here). You want to return the entire line so call race = file.readline().

Are you trying to read a single line, or all the lines? file.readline() will return the first line of the file as a string. If called again, it will return the second line, and so on. You can also load all the lines of the file as a list with file.readlines(), and then get the first or second element by using [0] or [1], so file.readlines()[1] will yield "Human".

if os.path.exists(saveDir + name + '.txt') == True:
print('welcome back ' + name + '.')
file = open(saveDir + name + '.txt')
race = file.readline() # this reads one line at a time
raceType = file.readline() # this will give you the second line (human)
else:
race = intro()

Why doesn't this writing to file in python work?

The idea behind the following code is that the if the variable crop is already contained within the .txt file the variable quantity will be added on to the end of the same line as crop. This is my attempt at doing this, however it doesn't work: you really need to run it to understand, but, essentially, the wrong section of the list is added to, an ever expanding series of '/' appear and the line breaks disappear. Does anyone know how to modify this code so it functions properly?
What should be outputted:
Lettuce 77 88 100
Tomato 99
What actually is outputted:
["['\\n', 'Lettuce 77 \\n88 ', 'Tomato 88 ']100 "]
Code:
def appendA ():
with open('alpha.txt', 'r') as file_1:
lines = file_1.readlines()
for line in lines:
if crop in line:
index = lines.index(line)
line = str(line + quantity + ' ')
lines [index] = line
newlines = str(lines)
#The idea here is that the variable quantity is added onto the end
# of the same row as the entered crop in the .txt file.
with open('alpha.txt', 'w') as file_3:
file_3.write (newlines)
def appendB ():
with open('alpha.txt', 'a') as file_2:
file_2.write ('\n')
file_2.write (crop + ' ')
file_2.write (quantity + ' ')
crop = input("Which crop? ")
quantity = input("How many? ")
with open('alpha.txt', 'a') as file_0:
if crop in open('alpha.txt').read():
appendA ()
else:
appendB ()

Let's start! Your code should look something like this:
def appendA():
with open('alpha.txt', 'r') as file_1:
lines = []
for line in file_1:
if crop in line:
line = str(line.rstrip("\n") + quantity + "\n")
lines.append(line)
#The idea here is that the variable quantity is added onto the end
# of the same row as the entered crop in the .txt file.
with open('alpha.txt', 'w') as file_3:
file_3.writelines(lines)
def appendB():
with open('alpha.txt', 'a') as file_2:
file_2.write('\n')
file_2.write(crop + ' ')
file_2.write(quantity + ' ')
crop = "Whichcrop"
quantity = "+!!!+"
with open('alpha.txt') as file_0:
if crop in file_0.read():
print("appendA")
appendA()
else:
print("appendB")
appendB()
with open('alpha.txt', 'a') as file_0:
if crop in open('alpha.txt').read():
appendA ()
else:
appendB ()
Also you make several mistakes.
This line "with open('alpha.txt', 'a') as file_0:" open file with context for append in the end of file, but you dont use variable file_0. I think it's extra.
On next step you opened file for check "crop in open('alpha.txt').read()", but never close it.
["['\n', 'Lettuce 77 \n88 ', 'Tomato 88 ']100 "]
You get such a output because, you use write instead of writelines:
with open('alpha.txt', 'w') as file_3:
file_3.write (newlines)
Also you write in the file after each iteration, better to form a list of strings and then write to file.

newlines = str(lines) # you convert all lines list to str - so you get default conversion
and also you should replace whole file if you want to write in the middle
And you can also get read of appendB, because you still check every line and your code anyway is not optimal in terms of performance :)
from os import remove, close
def appendA(filename, crop, quantity):
result = []
exists = False
with open(filename, 'r') as file_1:
lines = file_1.readlines()
for line in lines:
if not crop in line:
result.append(line)
else:
exists = True
result.append(line.strip('\n') + quantity + '\n')
if not exists:
with open(filename, 'a') as file_2:
file_2.write ('\n' + crop + ' ' + quantity + ' ')
else:
tmp_file = filename + '.tmp'
with open(tmp_file, 'w') as file_3:
file_3.write(result)
remove(filename)
move(tmp_file, filename)

"str(lines)": lines is list type, you can use ''.join(lines) to
convert it to a string.
"line in lines": "line" end with a "\n"
Code indent error: "line newlines = ''.join(lines)" and the follow
"if crop in lines" is mistake, if crop named "AA" and "AABB", the
new input "AA" with return true, the quantity will be appended to
all lines including "AA" ,not only the "AA" line.
def appendA():
with open('alpha.txt', 'r') as file_1:
lines = file_1.readlines()
for line in lines:
if crop in line:
index = lines.index(line)
line = str(line.replace("\n", "") + ' ' + quantity + '\n')
lines[index] = line
newlines = ''.join(lines)
# The idea here is that the variable quantity is added onto the end
# of the same row as the entered crop in the .txt file.
with open('alpha.txt', 'w') as file_3:
file_3.write(newlines)
def appendB():
with open('alpha.txt', 'a') as file_2:
file_2.write("\n")
file_2.write(crop + ' ')
file_2.write(quantity + ' ')
crop = input("Which crop? ")
quantity = input("How many? ")
with open('alpha.txt', 'a') as file_0:
if crop in open('alpha.txt').read():
appendA()
else:
appendB()