执行功能后，Python脚本返回意外的“无” [重复]

在python中，函数的默认返回值为

None

>>> def func():pass>>> print func()     #print or print() prints the return ValueNone>>> func()#remove print and the returned value is not printed. >>>

因此，只需使用：

letter_grade(score) #remove the print

另一种选择是将所有打印内容替换为

return

def letter_grade(score):    if 90 <= score <= 100:        return "A"    elif 80 <= score <= 89:        return "B"    elif 70 <= score <= 79:        return  "C"    elif 60 <= score <= 69:        return "D"    elif score < 60:        return "F"    else:        #This is returned if all other conditions aren't satisfied        return "Invalid Marks"

现在使用

print()

>>> print(letter_grade(91))A>>> print(letter_grade(45))F>>> print(letter_grade(75))C>>> print letter_grade(1000)Invalid Marks