I currently have some code that grabs all the lines after the first one in a file and saves it to the variable resourceslist . I want to add some code that says if there's only one line in the file then give variable resourceslist the value "oneline"
with open('filepaths', "r+") as f:
if index + 1 > len(f):
for _ in range(1):
next(f)
for lines in f:
resourceslist = f.read()
else:
resourceslist = "oneline"
You can write the following; your first for loop isn't necessary, as it will never actually loop, and the second one is unnecessary because you want to read the entire (remaining) contents of the file into resourceslist, without otherwise iterating over the remaining lines.
with open('filepath') as f:
next(f) # Skip the first line
resourceslist = f.read()
if not resourceslist: # i.e., f.read() returned the empty string
resourceslist = "oneline"
Related
I want to extract data from a file and change the value of an entry with a 'for-loop'.
f = open(r"C:\Users\Measurement\LOGGNSS.txt", "r")
x=0
content = [[],[]]
for line in f:
actualline = line.strip()
content.append(actualline.split(","))
x+=1
f.close
print(x)
for z in range(x):
print(z)
print(content[z][1])
IndexError: list index out of range
Using a real value instead of the variable 'z' works fine. But I need to change all first entries in the whole 2D-Array.
Why it does not work?
Your code has several problems.
First of all, use the with statement to open/close files correctly.
Then, you don't need to use a variable like x to keep track of the number of lines, just use enumerate() instead!
Here is how I would refactor your code to make it slimmer and more readable.
input_file = r"C:\Users\Measurement\LOGGNSS.txt"
content = []
with open(input_file, 'r') as f:
for line in f:
clean_line = line.strip().split(",")
content.append(clean_line)
for z, data in enumerate(content):
print(z,'\n',data)
Note that you could print the content while reading the file in one single loop.
with open(input_file, 'r') as f:
for z, line in enumerate(f):
clean_line = line.strip().split(",")
content.append(clean_line)
print(z,'\n', clean_line)
Finally, if you are dealing with a plain and simple csv file, then use the csv module from the standard library.
import csv
with open(input_file, 'r') as f:
content = csv.reader(f, delimiter=',')
You initialize your content with two empty arrays, so both of these will fail to find the first index ([1]), just initialize it with an empty array
content = []
I have the following problem. I am supposed to open a CSV file (its an excel table) and read it without using any library.
I tried already a lot and have now the first row in a tuple and this in a list. But only the first line. The header. But no other row.
This is what I have so far.
with open(path, 'r+') as file:
results=[]
text = file.readline()
while text != '':
for line in text.split('\n'):
a=line.split(',')
b=tuple(a)
results.append(b)
return results
The output should: be every line in a tuple and all the tuples in a list.
My question is now, how can I read the other lines in python?
I am really sorry, I am new to programming all together and so I have a real hard time finding my mistake.
Thank you very much in advance for helping me out!
This problem was many times on Stackoverflow so you should find working code.
But much better is to use module csv for this.
You have wrong indentation and you use return results after reading first line so it exits function and it never try read other lines.
But after changing this there are still other problems so it still will not read next lines.
You use readline() so you read only first line and your loop will works all time with the same line - and maybe it will never ends because you never set text = ''
You should use read() to get all text which later you split to lines using split("\n") or you could use readlines() to get all lines as list and then you don't need split(). OR you can use for line in file: In all situations you don't need while
def read_csv(path):
with open(path, 'r+') as file:
results = []
text = file.read()
for line in text.split('\n'):
items = line.split(',')
results.append(tuple(items))
# after for-loop
return results
def read_csv(path):
with open(path, 'r+') as file:
results = []
lines = file.readlines()
for line in lines:
line = line.rstrip('\n') # remove `\n` at the end of line
items = line.split(',')
results.append(tuple(items))
# after for-loop
return results
def read_csv(path):
with open(path, 'r+') as file:
results = []
for line in file:
line = line.rstrip('\n') # remove `\n` at the end of line
items = line.split(',')
results.append(tuple(items))
# after for-loop
return results
All this version will not work correctly if you will '\n' or , inside item which shouldn't be treated as end of row or as separtor between items. These items will be in " " which also can make problem to remove them. All these problem you can resolve using standard module csv.
Your code is pretty well and you are near goal:
with open(path, 'r+') as file:
results=[]
text = file.read()
#while text != '':
for line in text.split('\n'):
a=line.split(',')
b=tuple(a)
results.append(b)
return results
Your Code:
with open(path, 'r+') as file:
results=[]
text = file.readline()
while text != '':
for line in text.split('\n'):
a=line.split(',')
b=tuple(a)
results.append(b)
return results
So enjoy learning :)
One caveat is that the csv may not end with a blank line as this would result in an ugly tuple at the end of the list like ('',) (Which looks like a smiley)
To prevent this you have to check for empty lines: if line != '': after the for will do the trick.
I want to find the lines which start with a word of a list. If the word is found i want the line it stands in and the previous line to be deleted.
I am able to get the line and the previos one and print them but i can not get my head around not to pass them to my outputfile.
F.e.:
in-put:
This is not supposed to be deleted.
This shall be deleted.
Titel
This is not supposed to be deleted.
This is not supposed to be deleted
out-put:
This is not supposed to be deleted.
This is not supposed to be deleted.
This is not supposed to be deleted
I tried it with this code, but i keep getting a TypeError: 'str' object does not support item assignment
with open(file1) as f_in, open(file2, 'w') as f_out:
lines = f_in.read().splitlines()
for i, line in enumerate(lines):
clean = True
if line.startswith(('Text', 'Titel')):
for (line[i-1]) in lines:
clean = False
for line in lines:
clean =False
if clean == True:
f_out.write(line)
You don't have to read the file at once. Read the lines after each other, and store the current line, but write it out only after the next read, or not.
with open("file1") as finp, open("file2","w") as fout:
lprev=""
for line in finp:
if line.startswith("Titel") or line.startswith("Text"):
lprev=""
continue
if lprev:
fout.write(lprev)
lprev=line
if lprev:
fout.write(lprev) # write out the last line if needed
First keep track of which lines you want to copy:
lines_to_keep = []
with open(file1) as f_in:
deleted_previous_line = True
for line in f_in:
if line.startswith(('Text', 'Titel')):
if not deleted_previous_line:
del lines_to_keep[-1]
deleted_previous_line = True
continue
deleted_previous_line = False
lines_to_keep.append(line)
The trick with the deleted_previous_line is necessary to ensure it does not delete too many lines if consecutive lines start with 'Text' or 'Titel'.
Then write it to your output file
with open(file2, 'w') as f_out:
f_out.writelines(lines_to_keep)
How do you skip to the next lines of a file being looped line by line. This code below is skipping lines for the total count in the 2nd loop, I want it to skip the line 1 by 1 for the desired count so I can pull the right information from the file.
f = open("someTXT", "r")
lines = iter(f.readlines())
for line in lines:
thisLine = line.split(',')
if len(thisLine) > 3:
count = thisLine[4]
for i in range(1,int(count)):
next(lines)
print(line)
Here's a bit of code review. Not sure what you're asking though.
Use the context manager to open files:
with open("someTXT", 'rU') as f: # Universal newline flag, best practice
# lines = iter(f) # no need for this, my_file is an iterator
container = [] # use a container to hold your lines
for line in f:
test = test_for_correct_lines(line) # return True if keep and print
if test:
container.append(line)
# join the lines you want to keep with a newline and print them
print('\n'.join(container))
Question:
How can I open a file in python that contains one integer value per line. Make python read the file, store data in a list and then print the list?
I have to ask the user for a file name and then do everything above. The file entered by the user will be used as 'alist' in the function below.
Thanks
def selectionSort(alist):
for index in range(0, len(alist)):
ismall = index
for i in range(index,len(alist)):
if alist[ismall] > alist[i]:
ismall = i
alist[index], alist[ismall] = alist[ismall], alist[index]
return alist
I think this is exactly what you need:
file = open('filename.txt', 'r')
lines = [int(line.strip()) for line in file.readlines()]
print(lines)
I didn't use a with statement here, as I was not sure whether or not you intended to use the file further in your code.
EDIT: You can just assign an input to a variable...
filename = input('Enter file path: ')
And then the above stuff, except open the file using that variable as a parameter...
file = open(filename, 'r')
Finally, submit the list lines to your function, selectionSort.
selectionSort(lines)
Note: This will only work if the file already exists, but I am sure that is what you meant as there would be no point in creating a new one as it would be empty. Also, if the file specified is not in the current working directory you would need to specify the full path- not just the filename.
Easiest way to open a file in Python and store its contents in a string:
with open('file.txt') as f:
contents = f.read()
for your problem:
with open('file.txt') as f:
values = [int(line) for line in f.readlines()]
print values
Edit: As noted in one of the other answers, the variable f only exists within the indented with-block. This construction automatically handles file closing in some error cases, which you would have to do with a finally-construct otherwise.
You can assign the list of integers to a string or a list
file = open('file.txt', mode = 'r')
values = file.read()
values will have a string which can be printed directly
file = open('file.txt', mode = 'r')
values = file.readlines()
values will have a list for each integer but can't be printed directly
f.readlines() read all the lines in your file, but what if your file contains a lot of lines?
You can try this instead:
new_list = [] ## start a list variable
with open('filename.txt', 'r') as f:
for line in f:
## remove '\n' from the end of the line
line = line.strip()
## store each line as an integer in the list variable
new_list.append(int(line))
print new_list