Python 2.7 使用列表运行函数的问题

Question

在 Python 2.7 中，我的函数 pop(y,p) 的代码完美运行，但函数 aveChange(p,y) 返回多个打印行，我需要它只打印 1 行表示人口年平均变化的行。

而函数change(p,y,b) 只是说：

NameError: name 'b' is not defined

到目前为止我的代码如下：

def biggerThan():
    l=raw_input('Enter a list of numbers, separate each number with a    comma:').split(',')
    a=map(int,l)
    n=int(raw_input('Enter another number:'))
    a2=[i for i in a if i>n]
    print a2

    p = [151868, 153982, 156393, 158956, 161884, 165069, 168088, 
    171187, 174149, 177135, 179979, 182992, 185771, 188483, 
    191141, 193526, 195576, 197457, 199399, 201385, 203984, 
    206827, 209284, 211357, 213342, 215465, 217563, 219760, 
    222095, 224567, 227225, 229466, 231664, 233792, 235825, 
    237924, 240133, 242289, 244499, 246819, 249623]
    y1=1950
    y2=1991
    y=range(y1,y2)
def pop(y,p):
    fmt='{:<8}{:<20}{}'
    print(fmt.format('', 'Year', 'Population'))
    for i, (year, pop) in enumerate(zip(y, p)):
        print(fmt.format(i, year, pop))

def aveChange(p,y):
    p = [151868, 153982, 156393, 158956, 161884, 165069, 168088, 
    171187, 174149, 177135, 179979, 182992, 185771, 188483, 
    191141, 193526, 195576, 197457, 199399, 201385, 203984, 
    206827, 209284, 211357, 213342, 215465, 217563, 219760, 
    222095, 224567, 227225, 229466, 231664, 233792, 235825, 
    237924, 240133, 242289, 244499, 246819, 249623]
    y1=1950
    y2=1991
    y=range(y1,y2)
    yearly_change = []
    change=0.0
    total_change=0
    average_change=0
    for i in range(len(p)):
        p[i] = float(p[i])
        #calculate the change in population size for each two years
    for i in xrange(1,len(p)):
        change = p[i] - p[i-1]
        yearly_change.append(change) 
        total_change = float(sum(yearly_change))
        average_change = total_change/40
        print "The average annual change in population during the time period is",average_change

def change(p,y,b):
    p = [151868, 153982, 156393, 158956, 161884, 165069, 168088, 
    171187, 174149, 177135, 179979, 182992, 185771, 188483, 
    191141, 193526, 195576, 197457, 199399, 201385, 203984, 
    206827, 209284, 211357, 213342, 215465, 217563, 219760, 
    222095, 224567, 227225, 229466, 231664, 233792, 235825, 
    237924, 240133, 242289, 244499, 246819, 249623]
    y1=1950
    y2=1991
    y=range(y1,y2)
    yearly_change = []
    newchange=0.0
    greatest_increase=0
    smallest_increase=0
    greatest_year=0
    smallest_year=0
    BASE_YEAR=1950
    for i in range(1,len(p)):
        newchange = p[b] - p[b-1]
        yearly_change.append(newchange)

        if b==1:
            greatest_increase = newchange
            smallest_increase = newchange
            greatest_year = 1
            smallest_year = 1
        else:
            if newchange>greatest_increase:
                greatest_increase = newchange
                greatest_year = b
            elif newchange<smallest_increase:
                smallest_increase = newchange
                smallest_year = b
            print("The year with the greatest increase in population was",
                BASE_YEAR+greatest_year)
            print("The year with the smallest increase in population was",
                BASE_YEAR+smallest_year)

Answer 1

将您的 print 语句移到 for 循环之外的 aveChange(p,y) ：

for i in xrange(1,len(p)):
    change = p[i] - p[i-1]
    yearly_change.append(change) 
    total_change = float(sum(yearly_change))
    average_change = total_change/40
print "The average annual change in population during the time period is ",average_change

对于 change(p, y, b) 函数，请确保您使用 3 个参数调用它，并且您的所有参数都已定义！您收到错误是因为您使用b 调用函数，但在调用之前未在函数外部定义b！尝试这样称呼它：

change(p, y, 5)