python - Inconsistent use of tabs and spaces in indentation

Question

def contains_sequence(dna1, dna2):
    ''' (str, str) -> bool

    Return True if and only if DNA sequence dna2 occurs in the DNA sequence
    dna1.

    >>> contains_sequence('ATCGGC', 'GG')
    True
    >>> contains_sequence('ATCGGC', 'GT')
    False

    '''
    b=False
    len2=len(dna2)
    i=0
    for j in dna1:
        temp=dna1[i:i+len2]
        if temp == dna2:
            b=True
        i=i+1
    return b

I am new to Python. The program pasted above gives me an error "Inconsistent use of tabs and spaces in indentation" at line "if temp == dna2:" specifically. Can someone please help me out in finding out how the indentation is incorrect?

Answer 1

It means you have mixed up spaces and tabs in the indentation. You have to fix that to be consistent with either tabs or spaces.