[英]Python 2.7 Global name not defined
Writing a python program to perform merge sort, and I get a Global Name not found error 编写一个python程序来执行合并排序,但我得到一个找不到全局名称的错误
### Program for Merge Sort ###
def merge(numbers, l, m, r):
n1 = m-l-1 ### Size of the left side array ###
n2 = r-l ### Size of the right side array ###
### Temporary Lists ###
for i in range(n1):
L[i] = numbers[l+i]
for j in range(n2):
R[j] = numbers[m+j+1]
### The following code eliminates searching if any of the lists have become empty ###
L[n1] = float("inf")
R[n1] = float("inf")
i = 0
j = 0
for k in range(l,r+1):
if(L[i]<=R[j]):
numbers[k] = L[i]
i+=1
else:
numbers[k] = R[j]
j+=1
def mergeSort(numbers, l, r):
if (l<r):
m = l+(r-1)/2 ### Avoids overflow for large numbers
mergeSort(numbers, l, m)
mergeSort(numbers, m+1, r)
merge(numbers, l, m, r)
I have my driver program calling the mergeSort function on the user input numbers and when I run the code, I get an error saying Global Name 'R' is not defined 我的驱动程序在用户输入数字上调用mergeSort函数,运行代码时出现错误,提示未定义全局名称“ R”
Traceback (most recent call last):
File "merge_sort.py", line 55, in <module>
main()
File "merge_sort.py", line 50, in main
mergeSort(numbers, 0, size-1)
File "merge_sort.py", line 32, in mergeSort
mergeSort(numbers, l, m)
File "merge_sort.py", line 33, in mergeSort
mergeSort(numbers, m+1, r)
File "merge_sort.py", line 34, in mergeSort
merge(numbers, l, m, r)
File "merge_sort.py", line 10, in merge
R[j] = numbers[m+j+1]
NameError: global name 'R' is not defined`
What am I doing wrong? 我究竟做错了什么?
Indeed you never defined name R
. 实际上,您从未定义名称
R
Fix that by replacing: 通过替换来解决此问题:
for j in range(n2):
R[j] = numbers[m+j+1]
with: 有:
R = [numbers[m+j+1] for j in range(n2)]
(and similarly for L
, by the way -- I'm surprised you don't get that as an error since you access the name L
before the name R
). (顺便说一句,对于
L
,同样的方法-我很惊讶您没有将其视为错误,因为您在名称R
之前访问了名称L
)。
You need to initialize your temporary lists, L
and R
, before using them. 您需要先初始化临时列表
L
和R
,然后再使用它们。
L = []
R = []
for i in range(n1):
L[i] = numbers[l+i]
for j in range(n2):
R[j] = numbers[m+j+1]
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