生物信息学 - "global name 'start' is not defined" ？

Question

设计并编写一个可以检测跨膜结构域的程序，称为TMscanner.py。这个程序应该调用你编写的另外两个函数： getProteinRegion应该返回一个十个氨基酸窗口(最初抓取氨基酸 1-10，下一次抓取 2-20，依此类推(TMscanner还应该重复调用名为testForTM的第二个函数，该函数应计算并返回非极性十个氨基酸的小数部分。非极性氨基酸是 [A，V，L，I，P，M，F，W]

例：

protein = 'AVLIPMFWGSTNQYDEKRH' #Only the first 9 are nonpolar
results = tmScanner(protein)
print "Results are", results

它应该打印出来：

Results are [.8, .7, .6, .5, .4, .3, .2, .1, 0, 0]

-- #Test 代码

def getProteinRegion(protein, start):
#return first 10 aa in protein
    return protein[start:start+10]
def testForTM(protein):
#return ratio of nonpolar aa from a sample of first 10; move them up one step and repeat
    nonpolar = 0
    for aa in getProteinRegion(protein, start):
        if aa in ['A', 'V', 'L', 'I', 'P', 'M', 'F', 'W']:
            nonpolar = nonpolar + 1.0
    return nonpolar / 10.0

def tmSCANNER(protein):
#while the tested in testForTM is less than 10, append testforTM function to results; print results
    results = []
    start = 0
    while start <= 10:
        results = results.append(testForTM(protein))
        return results
        start = start + 1
##TESTING
#print getProteinRegion('AVLIPMFWGSTCNQYDEKRH')
#print testForTM('AVLIPMFW')
print tmSCANNER('AVLIPMFWGSTCNQYDEKRH')

--

Traceback (most recent call last):
  File "TMscanner.py", line 29, in <module>
    print tmSCANNER('AVLIPMFWGSTCNQYDEKRH')
  File "TMscanner.py", line 21, in tmSCANNER
    results = results.append(testForTM(protein))
  File "TMscanner.py", line 10, in testForTM
    for aa in getProteinRegion(protein, start):
NameError: global name 'start' is not defined

Answer 1

你的函数testForTM不带start参数，不声明名为start的局部变量，但它调用getProteinRegion(protein, start)。因此，Python 假设您必须使用全局变量，但您也没有具有该名称的全局变量。所以它提出了一个例外。

您可能想要的是添加start作为参数：

def testForTM(protein, start):

然后，在 tmSCANNER 内部的调用代码中，您确实有一个名为 start 的局部变量，这可能是您要作为 start 参数传递的值：

results = results.append(testForTM(protein, start))