如何跳过文件中的空行

Question

用Python 3写的程序：这是我第一次写涉及文件的程序。我需要忽略以#开头的注释行和空白行，然后把这些行分开，以便可以逐行处理。但是我总是遇到一个IndexError的错误信息，提示字符串索引超出范围，程序在空白行时崩溃。

import os.path

def main():

endofprogram = False
try:
    #ask user to enter filenames for input file (which would 
    #be animals.txt) and output file (any name entered by user)
    inputfile = input("Enter name of input file: ")

    ifile = open(inputfile, "r", encoding="utf-8")
#If there is not exception, start reading the input file        
except IOError:
    print("Error opening file - End of program")
    endofprogram = True

else:
    try:     
        #if the filename of output file exists then ask user to 
        #enter filename again. Keep asking until the user enters 
        #a name that does not exist in the directory        
        outputfile = input("Enter name of output file: ")
        while os.path.isfile(outputfile):
            if True:
                outputfile = input("File Exists. Enter name again: ")        
        ofile = open(outputfile, "w")

        #Open input and output files. If exception occurs in opening files in 
        #read or write mode then catch and report exception and 
        #exit the program
    except IOError:
        print("Error opening file - End of program")
        endofprogram = True            

if endofprogram == False:
    for line in ifile:
        #Process the file and write the result to display and to the output file
        line = line.strip()
        if line[0] != "#" and line != None:
            data = line.split(",")
            print(data)                
ifile.close()
ofile.close()
main() # Call the main to execute the solution

Answer 1

只需要在代码中用一个continue语句配合if条件就可以了：

if not line or line.startswith('#'):
    continue

这样的话，如果这一行是None（没有内容）、空的，或者以#开头，就会跳到下一行继续处理。

Answer 2

你的问题出在你认为空行是None，但其实不是。下面是一个可能的解决办法：

for line in ifile:
    line = line.strip()
    if not line:  # line is blank
        continue
    if line.startswith("#"):  # comment line
        continue
    data = line.split(',')
    # do stuff with data