为什么会出现索引超出范围错误？ 错误如下，

Question

Here is the error:

My code:

def isVariable(line):
    modifier = ['private','protected','public']
    datatype = ['String','int','float','boolean']
    status = False
    linelist = list(line.split())

    if(linelist[0] in modifier):
        if(linelist[1] in datatype):
            if(';' in linelist[len(linelist)-1]):
                status = True
                return status
    else:
        return status

f = open('Student.java','r')
vList = []

for line in f:
    status = isVariable(line)
    if status == True:
        vList.append(line)
  

print(vList)

What is wrong?

Answer 1

You get the error because in that line of code,

linelist is empty, and so, you cannot get the first (index 0 ) element of the list.

The reason a it can be empty is empty lines in the file.

Answer 2

It looks like one of the lines in your file is empty, so calling list(line.split()) returns an empty list. So, there is no zeroth element, casing the IndexError . You can add some try... except... blocks which will handle this error. Try:

def isVariable(line):
    modifier = ['private','protected','public']
    datatype = ['String','int','float','boolean']
    status = False
    linelist = list(line.split())
    
    try:
        has_modifier = linelist[0] in modifier
    except IndexError:
        return status

    try:
        has_datatype = linelist[1] in datatype
    except IndexError:
        return status

    try:
        has_semicolon = ';' in linelist[-1]
    except IndexError:
        return status

    if(has_modifier and has_datatype and has_semicolon):
        status = True
        return status
    else:
        return status


f =  open('Student.java','r')
vList = []

for line in f:
    status = isVariable(line)
    if status == True:
        vList.append(line)
    

print(vList)