我試圖通過下面定義的函數運行它來處理一些數據。它似乎可以很好地運行程序，但是循環不會迭代我期望的次數。我將 return 語句放在哪里似乎并不重要，只要它在函數內部而不是在 if 語句之下。我嘗試在每個 for 循環下獨立編寫行，并在每種情況下寫入預期的行數。def _ManhattanDistance(x,y): a = 0 for i in range(0,len(x)): a += abs(float(x[i])-float(y[i])) return adef _CabFare(x,y,z): with open(x, 'r') as f: with open(y, 'r') as g: with open(z, 'wb') as h: reader_1 = csv.reader(f) reader_2 = csv.reader(g) writer = csv.writer(h) for row_b in reader_2: for row_a in reader_1: if _ManhattanDistance(row_a,row_b) > 0: writer.writerow(row_a) writer.writerow(row_b) return作為參考，給定我的輸入 reader_1 應該有 200 行，而 reader_2 應該有 17145 行。由于我們的包含閾值為零，我預計輸出文件中有 17145*200 = 3429000 行——我得到的是一個 400 行的輸出。
2 回答
牛魔王的故事
TA貢獻1830條經驗 獲得超3個贊
這似乎有效：
from itertools import product
def _CabFare(x,y,z):
with open(x, 'r') as f, open(y, 'r') as g, open(z, 'wb') as h:
writer = csv.writer(h)
for row_a, row_b in product(csv.reader(f), csv.reader(g)):
if _ManhattanDistance(row_a, row_b) > 0:
writer.writerow(row_a)
writer.writerow(row_b)
速度較慢，但內存占用較少：
def _CabFare(x,y,z):
with open(x, 'r') as f, open(z, 'wb') as h:
writer = csv.writer(h)
for row_a in csv.reader(f):
with open(y, 'r') as g:
for row_b in csv.reader(g):
if _ManhattanDistance(row_a, row_b) > 0:
writer.writerow(row_a)
writer.writerow(row_b)
慕標琳琳
TA貢獻1830條經驗 獲得超9個贊
reader是一個有狀態的迭代器。一旦你用盡它，它就完成了，你需要重新打開它才能再次迭代文件：
def _CabFare(x,y,z):
with open(x, 'r') as f:
with open(y, 'r') as g:
with open(z, 'wb') as h:
reader_2 = csv.reader(g)
writer = csv.writer(h)
for row_b in reader_2:
reader_1 = csv.reader(f) # Reopen reader_1 for each iteration
for row_a in reader_1:
if _ManhattanDistance(row_a,row_b) > 0:
writer.writerow(row_a)
writer.writerow(row_b)
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