if条件判断

正确示范1

score = int(raw_input('input score: '))

if score >= 90:

    grade = 'A'

if score <90 and score >= 60:

    grade = 'B'

if score < 60:

    grade = 'C'

print '%d belongs to %s' % (score,grade)

 

正确示范2

score = int(raw_input('input score: '))

if score >= 90:

    grade = 'A'

elif score >= 60:

    grade = 'B'

else:

    grade = 'C'

print '%d belongs to %s' % (score,grade)

 

 

 

错误示范1

score = int(raw_input('input score: '))

if score >= 90:

    grade = 'A'

#下面的if和else作为一个组合了，会导致99 belongs to C。

if score <90 and score >= 60:

    grade = 'B'

else:

    grade = 'C'

print '%d belongs to %s' % (score,grade)

 

错误示范2

score = int(raw_input('input score: '))

if score >= 90:

    grade = 'A'

#下面的if和else作为一个组合了，会导致99 belongs to B。

if score >= 60:

    grade = 'B'

else:

    grade = 'C'

print '%d belongs to %s' % (score,grade)