如何逐个复制输入文件并在python中使用格式？

Question

I have been trying to copy the input file character by character and then trying to format them to avoid any kind of alignment issue. The first item in the input file is 50 characters long, the second item is 6 characters long, third is 3 characters long, fourth is 25 characters long, and the fifth is 4 characters long. I am not allowed to use list or tuple. The following is my code:

input_file=open('measles.txt','r')

f1=input('file name: ')

output_file=open(f1,'w')
for line in input_file:
    newstring=''
    line=line.strip()
    for ch in line:
        #I am trying to format the first two items in the input file
        print('{0:50}{51:57}'.format(line[0:50],line[51:57]),file=output_file)   

input_file.close()
output_file.close()

and the error I am getting is the following:

Traceback (most recent call last):
  File "C:/Users/Dasinator/Documents/Books IX/Python Examples/proj07.py", line 10, in <module>
    print('{0:50}{1:57}'.format(line[0:50],line[51:57]),file=output_file)
IndexError: tuple index out of range

Could anyone point out the error in the code and recommend ways to fix it? Thanks

Andorra                                           WB_HI                                             
Andorra                                           WB_HI                                             
Angola                                           WB_LMI                                            
Angola                                           WB_LMI                                            
Angola                                           WB_LMI   

The output still is not looking perfectly aligned.

This is how I modified my code and still having some trouble.

print('{0:50s}{1:6s}{2:<3s}{3:<25s}{4:<4s}'.format(line[0:50],line[50:56]),line[56:59],line[59:84],line[84:87],file=output_file)

and the output that I am getting is

Traceback (most recent call last):
  File "C:/Users/Dasinator/Documents/Books IX/Python Examples/proj07.py", line 10, in <module>
    print('{0:50s}{1:6s}{2:<3s}{3:<25s}{4:<4s}'.format(line[0:50],line[50:56]),line[56:59],line[59:84],line[84:87],file=output_file)
IndexError: tuple index out of range            

Answer 1

Looks like you've misunderstood how .format works, and what the formatting string should look like.

When you write a string " {0:50}{1:50}".format(stuff0, stuff1) the colon separates the index (before), from the number of characters that the string should take up when printed.

So, when you do:

print('{0:50}{51:57}'.format(line[0:50],line[51:57]),file=output_file)

you're telling python to use the 51st argument to .format. What you actually mean is the second argument to .format, or the 51st character in the string.

Presumably, what you actually want to do here is print the 0th-50th characters of the line, and the 51st-57th characters. That will look like:

print('{0:10}{1:10}'.format(line[0:50],line[51:57]),file=output_file)

Additionally, I don't know what you mean the file argument to do, but it's probably not going to do what you expect.

Answer 2

Why 51 here in second param: {0:50}{51:57} ?, should be 1 :

print('{0:50}{1:57}'.format(line[0:50],line[51:57]),file=output_file)
#            ^^^

As test:

>>> print('{0:10}{57:10}'.format(10,20))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IndexError: tuple index out of range
>>> print('{0:10}{1:10}'.format(10,20))
        10        20

To align second column to left side, use < char before width:

print('{0:50}{1:<57}'.format(line[0:50],line[51:57]),file=output_file)