Line Numbers

[wocosc]

Ok, lol.. I am back again. How can I get python to print line numbers if i have python already loading text from a .txt file. I just need it to print out the line numbers with the text that it is importing and printing.

[ghostdog74]

Ok, lol.. I am back again. How can I get python to print line numbers if i have python already loading text from a .txt file. I just need it to print out the line numbers with the text that it is importing and printing.

2 ways i can think of
1) use counter method eg

counter = 1
for line in open("file"):
     print counter, line
     counter +=1
 

2) use enumerate

for num,line in enumerate("file"):
    print num,line
 

[wocosc]

def display3():
    fname = raw_input("Enter a Filename: ")
    infile = open(fname, 'r')
    data = infile.read()
    print data
    counter = 1
    print counter, infile
    counter +=1 
 

so I would presume that this would work. However, when I run it, it does not print the numbers.. It prints the file, and then

"1 <open file 'auston', mode 'r' at 0x00C3D9F8>"

What did I do wrong?

[bartonc]

def display3():
    fname = raw_input("Enter a Filename: ")
    infile = open(fname, 'r')
    data = infile.read()
    print data
    counter = 1
    print counter, infile
    counter +=1 
 

so I would presume that this would work. However, when I run it, it does not print the numbers.. It prints the file, and then

"1 <open file 'auston', mode 'r' at 0x00C3D9F8>"

What did I do wrong?

Python has done exactly what you have asked for.
First, let's try to get you to start using "CODE" tags. Learn about them by reading the "POSTING GUIDELINES" on the right hand side of the page while you are posting (it there in "REPLY GUIDELINES" if you are replying). Thanks.
Second, as my friend ghostdog74 points out, two neat tricks are to use the in operator to iterate through the file for you and couple that with the enumerate built-in fuction:
Lastly, you don't have a loop set up, anyway:
One way to print line numbers from 1 to n:

def display3():
    fname = raw_input("Enter a Filename: ")
    infile = open(fname, 'r')
    counter = 0
    data = infile.read()
    while data:
        counter += 1
        print counter, data
        data = infile.read()
##    print counter, infile 
 

or, I'll bet you could modify this to do the same thing:

def display3():
    fname = raw_input("Enter a Filename: ")
    infile = open(fname, 'r')
##    counter = 0
##    data = infile.read()
    for i, data in enumerate(infile):
##    counter +=1
        print i, data
##    print counter, infile 
 

[runsun]

I tried the 1st one. It worked when using ...open('file'): in line 2.
But I have a further question:
How does this work:
read the 1st, 3rd ... lines, then output them in the 1st row (seperated by space);
read the 2nd, 4th ... lines, output in the 2nd row;
...

I used several loops. None of them worked.

2 ways i can think of
1) use counter method eg

counter = 1
for line in open("file"):
     print counter, line
     counter +=1
 

2) use enumerate

for num,line in enumerate("file"):
    print num,line
 

[bvdet]

I tried the 1st one. It worked when using ...open('file'): in line 2.
But I have a further question:
How does this work:
read the 1st, 3rd ... lines, then output them in the 1st row (seperated by space);
read the 2nd, 4th ... lines, output in the 2nd row;
...

I used several loops. None of them worked.

You may want to read the entire file and print them this way:

>>> fn = 'your_file'
>>> lineList = open(fn).readlines()
>>> odd_lines = [lineList[i] for i in range(len(lineList)) if i%2 == 1]
>>> even_lines = [lineList[i] for i in range(len(lineList)) if i%2 == 0]
>>> print ''.join(odd_lines)
...................................
>>> print ''.join(even_lines)
...................................
>>> 

OR

>>> odd_lines = [lineList[i] for i in range(0,len(lineList),2)]
>>> even_lines = [lineList[i] for i in range(1,len(lineList),2)]

You can also iterate:

>>> f = open(fn)
>>> odd_lines = []
>>> even_lines = []
>>> for i, line in enumerate(f):
...     if i%2 == 0:
...         odd_lines.append(line)
...     else:
...         even_lines.append(line)
...         
>>> f.close()

The above code creates a list of the even and odd lines and uses the string method join() to assemble the individual lines into one string. To get rid of the newline characters, use line.strip().

[runsun]

The first one works - it seperates odd and even lines. However, the odd_lines in the output are not in one row; so are the even_lines.

You may want to read the entire file and print them this way:

>>> fn = 'your_file'
>>> lineList = open(fn).readlines()
>>> odd_lines = [lineList[i] for i in range(len(lineList)) if i%2 == 1]
>>> even_lines = [lineList[i] for i in range(len(lineList)) if i%2 == 0]
>>> print ''.join(odd_lines)
...................................
>>> print ''.join(even_lines)
...................................
>>> 

OR

>>> odd_lines = [lineList[i] for i in range(0,len(lineList),2)]
>>> even_lines = [lineList[i] for i in range(1,len(lineList),2)]

You can also iterate:

>>> f = open(fn)
>>> odd_lines = []
>>> even_lines = []
>>> for i, line in enumerate(f):
...     if i%2 == 0:
...         odd_lines.append(line)
...     else:
...         even_lines.append(line)
...         
>>> f.close()

The above code creates a list of the even and odd lines and uses the string method join() to assemble the individual lines into one string. To get rid of the newline characters, use line.strip().

[bvdet]

The first one works - it seperates odd and even lines. However, the odd_lines in the output are not in one row; so are the even_lines.

They are not in one row when you print them because of the newline characters. You can strip the newline characters (and other whitespace characters as well) this way:

odd_lines = [lineList[i].strip() for i in range(0,len(lineList),2)]

Add a space in between this way:

print ' '.join(odd_lines)

[ghostdog74]

odd=[];even=[]
for num,line in enumerate(open("file")):
    if num%2==0: even.append(line.strip())
    elif num%2!=0: odd.append(line.strip())
print odd   
print even