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reading and deleting lines in python

I am trying to read all the lines in a specific file, and it prints the number of the line as an index.
What I am trying to do is to delete the line by inputting the number of the line by the user.
As far as it is now, it prints all the lines with the number of that line, but when I enter the number of the line to be deleted, it's not deleted.
This is the code of the delete function:
def deleteorders ():
index = 0
fh = open ('orders.txt', 'r')
lines = fh.readlines()
for line in lines:
lines = fh.readlines()
index = index+1
print (str(index) + ' ' + line)
try:
indexinp = int(input('Enter the number of the order to be deleted, or "B" to go back: '))
if indexinp == 'B':
return
else:
del line[indexinp]
print (line)
fh = open ('orders.txt', 'w')
fh.writelines(line)
fh.close()
except:
print ('The entered number is not in the range')
return

This should work (you'll need to add the error handling back in):
lines = enumerate(open('orders.txt'))
for i, line in lines:
print i, line
i = int(input(">"))
open('orders.txt', 'w').write(''.join((v for k, v in lines if k != i)))

Adding integers from a file

I'm writing a function that sums up integers from a file.
Here's the code:
def sum_integers_from_file(file_name):
try:
file = open(name)
total = 0
for i in file:
total += int(i)
file.close()
return total
except:
print "error"
file foo.txt:
1234
The function returns 1234.
why doesn't total += int(i) add up all the integers?

It is highly recommended to read files in a with statement. That frees you from the responsibility of closing the file and is also shorter! This works:
def sum_integers_from_file(file_name):
try:
with open(file_name, 'r') as f:
s = f.read()
total = 0
for char in s:
total += int(char)
return total
except:
print("error")

Your file has one line.
You're adding all ints from each line.
If you want to add 1,2,3,4 with that method move them to new lines
Also, you can do the same thing with this
with open(name) as f:
return sum(int(line) for line in f)

How do I count the number of lines that are full-line comments in python?

I'm trying to create a function that accepts a file as input and prints the number of lines that are full-line comments (i.e. the line begins with #followed by some comments).
For example a file that contains say the following lines should print the result 2:
abc
#some random comment
cde
fgh
#another random comment
So far I tried along the lines of but just not picking up the hash symbol:
infile = open("code.py", "r")
line = infile.readline()
def countHashedLines(filename) :
while line != "" :
hashes = '#'
value = line
print(value) #here you will get all
#if(value == hashes): tried this but just wasn't working
# print("hi")
for line in value:
line = line.split('#', 1)[1]
line = line.rstrip()
print(value)
line = infile.readline()
return()
Thanks in advance,
Jemma

I re-worded a few statements for ease of use (subjective) but this will give you the desired output.
def countHashedLines(lines):
tally = 0
for line in lines:
if line.startswith('#'): tally += 1
return tally
infile = open('code.py', 'r')
all_lines = infile.readlines()
num_hash_nums = countHashedLines(all_lines) # <- 2
infile.close()
...or if you want a compact and clean version of the function...
def countHashedLines(lines):
return len([line for line in lines if line.startswith('#')])

I would pass the file through standard input
import sys
count = 0
for line in sys.stdin: """ Note: you could also open the file and iterate through it"""
if line[0] == '#': """ Every time a line begins with # """
count += 1 """ Increment """
print(count)

Here is another solution that uses regular expressions and will detect comments that have white space in front.
import re
def countFullLineComments(infile) :
count = 0
p = re.compile(r"^\s*#.*$")
for line in infile.readlines():
m = p.match(line)
if m:
count += 1
print(m.group(0))
return count
infile = open("code.py", "r")
print(countFullLineComments(infile))

Evaluating the next line in a For Loop while in the current iteration

Here is what I am trying to do:
I am trying to solve an issue that has to do with wrapping in a text file.
I want to open a txt file, read a line and if the line contains what I want it to contain, check the next line to see if it does not contain what is in the first line. If it does not, add the line to the first line.
import re
stuff = open("my file")
for line in stuff:
if re.search("From ", line):
first = line
print first
if re.search('From ', handle.next()):
continue
else: first = first + handle.next()
else: continue
I have looked a quite a few things and cannot seem to find an answer. Please help!

I would try to do something like this, but this is invalid for triples of "From " and not elegant at all.
lines = open("file", 'r').readlines()
lines2 = open("file2", 'w')
counter_list=[]
last_from = 0
for counter, line in enumerate(lines):
if "From " in line and counter != last_from +1:
last_from = counter
current_count = counter
if current_count+1 == counter:
if "From " in line:
counter_list.append(current_count+1)
for counter, line in enumerate(lines):
if counter in counter_list:
lines2.write(line)
else:
lines2.write(line, '\n')
Than you can check the lines2 if its helped.
You could also revert order of lines, then check in next line not in previous. That would solve your problem in one loop.

Thank you Martjin for helping me reset my mind frame! This is what I came up with:
handle = open("my file")
first = ""
second = ""
sent = ""
for line in handle:
line = line.rstrip()
if len(first) > 0:
if line.startswith("From "):
if len(sent) > 0:
print sent
else: continue
first = line
second = ""
else:
second = second + line
else:
if line.startswith("From "):
first = line
sent = first + second
It is probably crude, but it definitely got the job done!

#list index out of range

def isexact(pat):
for c in pat.upper():
if c not in 'ATGC':
return 0
return 1
def print_matches(ofh, enz, matches):
if matches:
print >>ofh, "Enzyme %s matches at:" % enz,
for m in matches:
print >>ofh, m,
print >>ofh
else:
print >>ofh, "No match found for enzyme %s." % enz
def get_site_only(pat):
newpat = ""
for c in pat:
if c.isalpha():
newpat += c
return newpat
def findpos(seq, pat):
matches = []
current_match = seq.find(pat)
while current_match != -1:
matches.append(current_match)
current_match =seq.find(pat, current_match+1)
return matches
seq = ""
ifh = open("C:\Python27\\link_cutzymes.txt",'r')
ofh = open("C:\Python27\\re-en-output.txt", "w")
line = ifh.readline()
while line:
fields = line.split()
name = fields[0]
pat = get_site_only(fields[2])
if isexact(pat):
print_matches(ofh, name, findpos(seq, pat))
line = ifh.readline()
else:
line = ifh.readline()
ofh.close()
ifh.close()
it is showing list index error can help me
Traceback (most recent call last): File
"C:/Users/ram/Desktop/rest_enz7.py", line 55, in
name = fields[0] IndexError: list index out of range

name = fields[0] - you probably are reading an empty line, splitting it, and accessing it at index 0, which is out of range for an empty list..
you can make sure your file contains only lines of your format, check for empty lines in the code, or use try and except to name a few options.

while reading the data from file,if data is not exist to split,it will not convert into list. I can see in your code name = fields[0] is causing error.
At that time please use try and except in your code.
you can rewrite the code as :
try:
fields = line.split()
name = fields[0]
except:
pass

What a string[x] does is get the xth letter of the list. This means that if there is no object in the xth position then you get an error.
So if name = fields[0] returns an error then fieldsmust be an empty list (It would look like this: []) because there is no first object (Python counts from zero so letter 0 is letter 1, letter 1 is letter 2 and so on). You can fix this with a try: and except: like so:
try:
name = fields[0]
except:
name = '' #Or whatever code you want to run if it fails
In the place of name = fields[0]