Let say I have a file with 48,222 lines. I then give an index value, let say, 21,000.
Is there any way in Python to "move" the contents of the file starting from index 21,000 such that now I have two files: the original one and the new one. But the original one now is having 21,000 lines and the new one 27,222 lines.
I read this post which uses partition and is quite describing what I want:
with open("inputfile") as f:
contents1, sentinel, contents2 = f.read().partition("Sentinel text\n")
with open("outputfile1", "w") as f:
f.write(contents1)
with open("outputfile2", "w") as f:
f.write(contents2)
Except that (1) it uses "Sentinel Text" as separator, (2) it creates two new files and require me to delete the old file. As of now, the way I do it is like this:
for r in result.keys(): #the filenames are in my dictionary, don't bother that
f = open(r)
lines = f.readlines()
f.close()
with open("outputfile1.txt", "w") as fn:
for line in lines[0:21000]:
#write each line
with open("outputfile2.txt", "w") as fn:
for line in lines[21000:]:
#write each line
Which is quite a manual work. Is there a built-in or more efficient way?
You can also use writelines() and dump the sliced list of lines from 0 to 20999 into one file and another sliced list from 21000 to the end into another file.
with open("inputfile") as f:
content = f.readlines()
content1 = content[:21000]
content2 = content[21000:]
with open("outputfile1.txt", "w") as fn1:
fn1.writelines(content1)
with open('outputfile2.txt','w') as fn2:
fn2.writelines(content2)
Related
I have 5 files from which i want to take each line (24 lines in total) and save it to a new file. I managed to find a code which will do that but they way it is, every time i have to manually change the number of the appropriate original file and of the file i want to save it to and also the number of each line every time.
The code:
x1= np.loadtxt("x_p2_40.txt")
x2= np.loadtxt("x_p4_40.txt")
x3= np.loadtxt("x_p6_40.txt")
x4= np.loadtxt("x_p8_40.txt")
x5= np.loadtxt("x_p1_40.txt")
with open("x_p1_40.txt", "r") as file:
content = file.read()
first_line = content.split('\n', 1)[0]
with open("1_p_40_x.txt", "a" ) as f :
f.write("\n")
with open("1_p_40_x.txt", "a" ) as fa :
fa.write(first_line)
print(first_line)
I am a beginner at python, and i'm not sure how to make a loop for this, because i assume i need a loop?
Thank you!
Since you have multiple files here, you could define their names in a list, and use a list comprehension to open file handles to them all:
input_files = ["x_p2_40.txt", "x_p4_40.txt", "x_p6_40.txt", "x_p8_40.txt", "x_p1_40.txt"]
file_handles = [open(f, "r") for f in input_files]
Since each of these file handles is an iterator that yields a single line every time you iterate over it, you could simply zip() all these file handles to iterate over them simultaneously. Also throw in an enumerate() to get the line numbers:
for line_num, files_lines in enumerate(zip(*file_handles), 1):
out_file = f"{line_num}_p_40.txt"
# Remove trailing whitespace on all lines, then add a newline
files_lines = [f.rstrip() + "\n" for f in files_lines]
with open(out_file, "w") as of:
of.writelines(files_lines)
With three files:
x_p2_40.txt:
2_1
2_2
2_3
2_4
x_p4_40.txt:
4_1
4_2
4_3
4_4
x_p6_40.txt:
6_1
6_2
6_3
6_4
I get the following output:
1_p_40.txt:
2_1
4_1
6_1
2_p_40.txt:
2_2
4_2
6_2
3_p_40.txt:
2_3
4_3
6_3
4_p_40.txt:
2_4
4_4
6_4
Finally, since we didn't use a context manager to open the original file handles, remember to close them after we're done:
for fh in file_handles:
fh.close()
If you have files with an unequal number of lines and you want to create files for all lines, consider using itertools.zip_longest() instead of zip()
In order to read each of your input files, you can store them in a list and iterate over it with a for loop. Then we add every line to a single list with the function extend() :
inputFiles = ["x_p2_40.txt", "x_p4_40.txt", "x_p6_40.txt", "x_p8_40.txt", "x_p1_40.txt"]
outputFile = "outputfile.txt"
lines = []
for filename in inputFiles:
with open(filename, 'r') as f:
lines.extend(f.readlines())
lines[-1] += '\n'
Finally you can write all the line to your output file :
with open(outputFile, 'w') as f:
f.write(''.join(lines))
I'm trying to have output to be without commas, and separate each line into two strings and print them.
My code so far yields:
173,70
134,63
122,61
140,68
201,75
222,78
183,71
144,69
But i'd like it to print it out without the comma and the values on each line separated as strings.
if __name__ == '__main__':
# Complete main section of code
file_name = "data.txt"
# Open the file for reading here
my_file = open('data.txt')
lines = my_file.read()
with open('data.txt') as f:
for line in f:
lines.split()
lines.replace(',', ' ')
print(lines)
In your sample code, line contains the full content of the file as a str.
my_file = open('data.txt')
lines = my_file.read()
You then later re-open the file to iterate the lines:
with open('data.txt') as f:
for line in f:
lines.split()
lines.replace(',', ' ')
Note, however, str.split and str.replace do not modify the existing value, as strs in python are immutable. Also note you are operating on lines there, rather than the for-loop variable line.
Instead, you'll need to assign the result of those functions into new values, or give them as arguments (E.g., to print). So you'll want to open the file, iterate over the lines and print the value with the "," replaced with a " ":
with open("data.txt") as f:
for line in f:
print(line.replace(",", " "))
Or, since you are operating on the whole file anyway:
with open("data.txt") as f:
print(f.read().replace(",", " "))
Or, as your file appears to be CSV content, you may wish to use the csv module from the standard library instead:
import csv
with open("data.txt", newline="") as csvfile:
for row in csv.reader(csvfile):
print(*row)
with open('data.txt', 'r') as f:
for line in f:
for value in line.split(','):
print(value)
while python can offer us several ways to open files this is the prefered one for working with files. becuase we are opening the file in lazy mode (this is the prefered one espicialy for large files), and after exiting the with scope (identation block) the file io will be closed automaticly by the system.
here we are openening the file in read mode. files folow the iterator polices, so we can iterrate over them like lists. each line is a true line in the file and is a string type.
After getting the line, in line variable, we split (see str.split()) the line into 2 tokens, one before the comma and the other after the comma. split return new constructed list of strings. if you need to omit some unwanted characters you can use the str.strip() method. usualy strip and split combined together.
elegant and efficient file reading - method 1
with open("data.txt", 'r') as io:
for line in io:
sl=io.split(',') # now sl is a list of strings.
print("{} {}".format(sl[0],sl[1])) #now we use the format, for printing the results on the screen.
non elegant, but efficient file reading - method 2
fp = open("data.txt", 'r')
line = None
while (line=fp.readline()) != '': #when line become empty string, EOF have been reached. the end of file!
sl=line.split(',')
print("{} {}".format(sl[0],sl[1]))
Sorry for daft newbie question but my nested loops wont work. It returns only the first iteration. What have I missed??
I'm trying to grep for a multiple strings in my main file. I think I messed up the indentation but all the variations I try return errors.
f = open('GRCh37_genes_all_mod.txt', 'rU') # main search file
f1 = open('genes_regions_out.txt', 'a') #out file
f2 = open('gene_list.txt', 'r') # search list
for gene in f2:
for line in f:
if gene in line:
print line
f1.write(line)
You can only iterate through a file once. After the first time through f, the next time you try and run for line in f, you won't get any content.
If you want to iterate through a file's content multiple times, you can put that content into a list.
with open('GRCh37_genes_all_mod.txt', 'rU') as f:
contents = list(f)
with open('gene_list.txt', 'r') as f:
genes = list(f)
for gene in genes:
for line in contents:
...
After the first iteration, the file pointer is at the end of the file and the iterator is exhausted (calls to next(f) will raise StopIteration).
The simplest solution for this case is to reset the file pointer using f.seek(0):
for gene in f2:
f.seek(0)
for line in f:
# ...
For other iterables (that might not be 'resetable'), if you know how many 'copies' you need, you can use itertools.tee(), or, if you know the iterable is finite (some iterable are infinite) and all it's content will fit in memory, you can just make a list of it as explained by Khelwood.
I have a test.txt file that contains:
yellow.blue.purple.green
red.blue.red.purple
And i'd like to have on output.txt just the second and the third part of each line, like this:
blue.purple
blue.red
Here is python code:
with open ('test.txt', 'r') as file1, open('output.txt', 'w') as file2:
for line in file1:
file2.write(line.partition('.')[2]+ '\n')
but the result is:
blue.purple.green
blue.red.purple
How is possible take only the second and third part of each line?
Thanks
You may want
with open('test.txt', 'r') as file1, open('output.txt', 'w') as file2:
for line in file1:
file2.write(".".join(line.split('.')[1:3])+ '\n')
When you apply split('.') to the line e.g. yellow.blue.purple.green, you get a list of values
["yellow", "blue", "purple", "green"]
By slicing [1:3], you get the second and third items.
First I created a .txt file that had the same data that you entered in your original .txt file. I used the 'w' mode to write the data as you already know. I create an empty list as well that we will use to store the data, and later write to the output.txt file.
output_write = []
with open('test.txt', 'w') as file_object:
file_object.write('yellow.' + 'blue.' + 'purple.' + 'green')
file_object.write('\nred.' + 'blue.' + 'red.' + 'purple')
Next I opened the text file that I created and used 'r' mode to read the data on the file, as you already know. In order to get the output that you wanted, I read each line of the file in a for loop, and for each line I split the line to create a list of the items in the line. I split them based on the period in between each item ('.'). Next you want to get the second and third items in the lines, so I create a variable that stores index[1] and index[2] called new_read. After we will have the two pieces of data that you want and you'll likely want to write to your output file. I store this data in a variable called output_data. Lastly I append the output data to the empty list that we created earlier.
with open ('test.txt', 'r') as file_object:
for line in file_object:
read = line.split('.')
new_read = read[1:3]
output_data = (new_read[0] + '.' + new_read[1])
output_write.append(output_data)
Lastly we can write this data to a file called 'output.txt' as you noted earlier.
with open('output.txt', 'w') as file_object:
file_object.write(output_write[0])
file_object.write('\n' + output_write[1])
print(output_write[0])
print(output_write[1])
Lastly I print the data just to check the output:
blue.purple
blue.red
I have a file that I am currently reading from using
fo = open("file.txt", "r")
Then by doing
file = open("newfile.txt", "w")
file.write(fo.read())
file.write("Hello at the end of the file")
fo.close()
file.close()
I basically copy the file to a new one, but also add some text at the end of the newly created file. How would I be able to insert that line say, in between two lines separated by an empty line? I.e:
line 1 is right here
<---- I want to insert here
line 3 is right here
Can I tokenize different sentences by a delimiter like \n for new line?
First you should load the file using the open() method and then apply the .readlines() method, which splits on "\n" and returns a list, then you update the list of strings by inserting a new string in between the list, then simply write the contents of the list to the new file using the new_file.write("\n".join(updated_list))
NOTE: This method will only work for files which can be loaded in the memory.
with open("filename.txt", "r") as prev_file, open("new_filename.txt", "w") as new_file:
prev_contents = prev_file.readlines()
#Now prev_contents is a list of strings and you may add the new line to this list at any position
prev_contents.insert(4, "\n This is a new line \n ")
new_file.write("\n".join(prev_contents))
readlines() is not recommended because it reads the whole file into memory. It is also not needed because you can iterate over the file directly.
The following code will insert Hello at line 2 at line 2
with open('file.txt', 'r') as f_in:
with open('file2.txt','w') as f_out:
for line_no, line in enumerate(f_in, 1):
if line_no == 2:
f_out.write('Hello at line 2\n')
f_out.write(line)
Note the use of the with open('filename','w') as filevar idiom. This removes the need for an explicit close() because it closes the file automatically at the end of the block, and better, it does this even if there is an exception.
For Large file
with open ("s.txt","r") as inp,open ("s1.txt","w") as ou:
for a,d in enumerate(inp.readlines()):
if a==2:
ou.write("hi there\n")
ou.write(d)
U could use a marker
#FILE1
line 1 is right here
<INSERT_HERE>
line 3 is right here
#FILE2
some text
with open("FILE1") as file:
original = file.read()
with open("FILE2") as input:
myinsert = input.read()
newfile = orginal.replace("<INSERT_HERE>", myinsert)
with open("FILE1", "w") as replaced:
replaced.write(newfile)
#FILE1
line 1 is right here
some text
line 3 is right here