怎么實(shí)現(xiàn)Python列表去重復(fù)項(xiàng)

## 1. 新建列表，如果新列表中不存在，則添加到新列表。 
def unique(data): 
 new_list = [] 
 for item in data: 
 if item not in new_list: 
  new_list.append(item) 
 return new_list 
# test 
data = ['a', 'a', 1, 1, 2, 2, 'b', 'b', 2, 1] 
start_time = time.time() 
print("new_list + not in data:", unique(data)) 
print("time:" + str((time.time() - start_time) * 1000) + " ms") 
# result 
$ python -V 
Python 2.7.16 
$ python unique.py 
('for list + not in. data:', ['a', 1, 2, 'b']) 
time:0.0441074371338 ms 
## 2. 新建列表。根據(jù)下標(biāo)判斷是否存在新列表中，如果新列表中不存在則添加到新列表。 
def unique(data): 
 new_list = [] 
 for i in range(len(data)): 
 if data[i] not in new_list: 
  new_list.append(data[i]) 
 return new_list 
## 2.1 新建列表，使用列表推導(dǎo)來去重。是前一種的簡寫。 
def unique(data): 
 new_list = [] 
 [new_list.append(i) for i in data if not i in new_list] 
 return new_list 
# test 
data = ['a', 'a', 1, 1, 2, 2, 'b', 'b', 2, 1] 
start_time = time.time() 
print("for range + not in. data:", unique(data)) 
print("time:" + str((time.time() - start_time) * 1000) + " ms") 
## 3. 通過index找不到該項(xiàng)，則追加到新列表中。index找不到會(huì)報(bào)錯(cuò)，因此放在異常處理里。 
def unique(data): 
 new_list = [] 
 for i in range(len(data)): 
 item = data[i] 
 try: 
  if (new_list.index(item) < 0): 
  print('new_list:', new_list) 
 except ValueError: 
  new_list.append(item) 
 return new_list 
# test 
data = ['a', 'a', 1, 1, 2, 2, 'b', 'b', 2, 1] 
start_time = time.time() 
print("list index + except:", unique(data)) 
print("time:" + str((time.time() - start_time) * 1000) + " ms") 
## 4. 新建列表，兩個(gè)循環(huán)。如果內(nèi)循環(huán)與外循環(huán)項(xiàng)相同，且下標(biāo)相同就添加到新列表，其余忽略 
def unique(data): 
 new_list = [] 
 for i in range(len(data)): 
 j = 0 
 while j <= i: 
  if data[i] == data[j]: 
  if i == j: 
   new_list.append(data[i]) 
  break 
  j += 1 
 return new_list 
# test 
data = ['a', 'a', 1, 1, 2, 2, 'b', 'b', 2, 1] 
start_time = time.time() 
print("new list + for. new_list:", unique(data)) 
print("time:" + str((time.time() - start_time) * 1000) + " ms") 
## 5. 在原有列表上移除重復(fù)項(xiàng)目。自后往前遍歷，逐個(gè)與前面項(xiàng)比較，如果值相同且下標(biāo)相同，則移除當(dāng)前項(xiàng)。 
def unique(data): 
 l = len(data) 
 while (l > 0): 
 l -= 1 
 i = l 
 while i > 0: 
  i -= 1 
  if data[i] == data[l]: 
  del data[l] 
  break 
 return data 
# test 
data = ['a', 'a', 1, 1, 2, 2, 'b', 'b', 2, 1] 
start_time = time.time() 
print("one list while. last -> first result. data:", unique(data)) 
print("time:" + str((time.time() - start_time) * 1000) + " ms") 
## 6. 在原有列表上移除重復(fù)項(xiàng)目。自前往后遍歷，逐個(gè)與后面項(xiàng)比較，如果值相同且下標(biāo)相同，則移除當(dāng)前項(xiàng)。 
def unique(data): 
 l = len(data) 
 i = 0 
 while i < l: 
 j = i + 1 
 while j < l: 
  if data[i] == data[j]: 
  del data[j] 
  l -= 1 
  i -= 1 
  break 
  j += 1 
 i += 1 
 return data 
# test 
data = ['a', 'a', 1, 1, 2, 2, 'b', 'b', 2, 1] 
start_time = time.time() 
print("one list while. first -> last result. data:", unique(data)) 
print("time:" + str((time.time() - start_time) * 1000) + " ms") 
## 7. 新建列表。遍歷列表，利用index比較出現(xiàn)的位置，如果出現(xiàn)在第一次的位置則追加到新數(shù)組。 
def unique(data): 
 new_list = [] 
 for i in range(len(data)): 
 if i == data.index(data[i]): 
  new_list.append(data[i]) 
 return new_list 
# test 
data = ['a', 'a', 1, 1, 2, 2, 'b', 'b', 2, 1] 
start_time = time.time() 
print("for range + index. data:", unique(data)) 
print("time:" + str((time.time() - start_time) * 1000) + " ms") 
## 8. 利用字典屬性唯一性來實(shí)現(xiàn)去重復(fù)。 
def unique(data): 
 obj = {} 
 for item in data: 
 obj[item] = item 
 return obj.values() 
# test 
data = ['a', 'a', 1, 1, 2, 2, 'b', 'b', 2, 1] 
start_time = time.time() 
print("list + dict:", unique(data)) 
print("time:" + str((time.time() - start_time) * 1000) + " ms") 
## 或者直接通過dict.fromkeys來實(shí)現(xiàn) 
print("dict fromkeys:", dict.fromkeys(data).keys()) 
## 9. 利用filter函數(shù)，即把不符合條件的過濾掉。這里filter不支持下標(biāo)，因此需要借助外部列表存儲(chǔ)不重復(fù)項(xiàng) 
def uniq(item): 
 i = data.index(item) 
 if (item not in new_list): 
 new_list.append(item) 
 return True 
 return False 
def unique(item): 
 if obj.get(item) == None: 
 obj[item] = item 
 return True 
 return False 
# test 
data = ['a', 'a', 1, 1, 2, 2, 'b', 'b', 2, 1] 
start_time = time.time() 
new_list = [] 
print('filter + list + not in: ', filter(uniq, data)) 
print("time:" + str((time.time() - start_time) * 1000) + " ms") 
## 10. 利用字典結(jié)合過濾來實(shí)現(xiàn)去重復(fù)。 
def unique(item): 
 if obj.get(item) == None: 
 obj[item] = item 
 return True 
 return False 
# test 
data = ['a', 'a', 1, 1, 2, 2, 'b', 'b', 2, 1] 
start_time = time.time() 
obj = {} 
print("filter + dict + get:", filter(unique, data)) 
print("time:" + str((time.time() - start_time) * 1000) + " ms") 
## 11. 利用map來實(shí)現(xiàn)去重復(fù)。與map與filter類似，是一個(gè)高階函數(shù)。可以針對(duì)其中項(xiàng)逐個(gè)修改操作。 
## 與filter不同map會(huì)保留原有項(xiàng)目，并不會(huì)刪除，因此值可以改為None，然后再過濾掉。 
def unique(item): 
 if item not in new_list: 
 new_list.append(item) 
 return item 
 return None 
# test 
data = ['a', 'a', 1, 1, 2, 2, 'b', 'b', 2, 1] 
new_list = [] 
start_time = time.time() 
print("list from Map:", filter(lambda item: item != None, map(unique, data))) 
print("time:" + str((time.time() - start_time) * 1000) + " ms") 
## 12. 利用set數(shù)據(jù)結(jié)構(gòu)里key的唯一性來去重復(fù) 
data = ['a', 'a', 1, 1, 2, 2, 'b', 'b', 2, 1] 
print("from Set:", list(set(data))) 
print("time:" + str((time.time() - start_time) * 1000) + " ms") 
## 13. 提前排序，從后向前遍歷，將當(dāng)前項(xiàng)與前一項(xiàng)對(duì)比，如果重復(fù)則移除當(dāng)前項(xiàng) 
def unique(data): 
 data.sort() 
 l = len(data) 
 while (l > 0): 
 l -= 1 
 if (data[l] == data[l - 1]): 
  data.remove(data[l]) 
 return data 
# test 
data = ['a', 'a', 1, 1, 2, 2, 'b', 'b', 2, 1] 
start_time = time.time() 
print("sort + remove:", unique(data)) 
print("time:" + str((time.time() - start_time) * 1000) + " ms") 
## 14. 提前排序，自前往后遍歷，將當(dāng)前項(xiàng)與后一項(xiàng)對(duì)比，如果重復(fù)則移除當(dāng)前項(xiàng) 
def unique(data): 
 """ 
 in python 3: TypeError: '<' not supported between instances of 'int' and 'str' 
 need to keep the same Type of member in List 
 """ 
 data.sort() 
 l = len(data) - 1 
 i = 0 
 while i < l: 
 if (data[i] == data[i + 1]): 
  del data[i] 
  i -= 1 
  l -= 1 
 i += 1 
 return data 
# test 
data = ['a', 'a', 1, 1, 2, 2, 'b', 'b', 2, 1] 
start_time = time.time() 
print("sort+del ASE:", unique(data)) 
print("time:" + str((time.time() - start_time) * 1000) + " ms") 
## 15. 利用reduce函數(shù)來去重復(fù)。reduce具有累計(jì)的作用，判斷如果不在累計(jì)結(jié)果中出現(xiàn)，則追加到結(jié)果中。 
import functools 
def unique(data): 
 new_list = [] 
 def foo(result, item): 
 if isinstance(result, list) == False: 
  result = [result] 
 return result if item in result else result + [item] 
 return functools.reduce(foo, data) 
# test 
data = ['a', 'a', 1, 1, 2, 2, 'b', 'b', 2, 1] 
start_time = time.time() 
print("functools.reduce:", unique(data)) 
print("time:" + str((time.time() - start_time) * 1000) + " ms") 
## 16. 利用遞歸調(diào)用來去重復(fù)。遞歸自后往前逐個(gè)調(diào)用，當(dāng)長度為1時(shí)終止。 
## 當(dāng)后一項(xiàng)與前任一項(xiàng)相同說明有重復(fù)，則刪除當(dāng)前項(xiàng)。相當(dāng)于利用自我調(diào)用來替換循環(huán) 
def recursion_unique(data, len): 
 if (len <= 1): 
 return data 
 l = len 
 last = l - 1 
 is_repeat = False 
 while (l > 1): 
 l -= 1 
 if (data[last] == data[l - 1]): 
  is_repeat = True 
  break 
 if (is_repeat): 
 del data[last] 
 return recursion_unique(data, len - 1) 
# test 
data = ['a', 'a', 1, 1, 2, 2, 'b', 'b', 2, 1] 
start_time = time.time() 
print("recursion_unique:", recursion_unique(data, len(data))) 
print("time:" + str((time.time() - start_time) * 1000) + " ms") 
## 17. 利用遞歸調(diào)用來去重復(fù)的另外一種方式。遞歸自后往前逐個(gè)調(diào)用，當(dāng)長度為1時(shí)終止。 
## 與上一個(gè)遞歸不同，這里將不重復(fù)的項(xiàng)目作為結(jié)果拼接起來 
def recursion_unique_new(data, len): 
 if (len <= 1): 
 return data 
 l = len 
 last = l - 1 
 is_repeat = False 
 while (l > 1): 
 l -= 1 
 if (data[last] == data[l - 1]): 
  is_repeat = True 
  break 
 if (is_repeat): 
 del data[last:] 
 result = [] 
 else: 
 result = [data[last]] 
 return recursion_unique_new(data, len - 1) + result 
# test 
data = ['a', 'a', 1, 1, 2, 2, 'b', 'b', 2, 1] 
start_time = time.time() 
print("recursion_unique_new:", recursion_unique_new(data, len(data))) 
print("time:" + str((time.time() - start_time) * 1000) + " ms") 
## 18. 利用numpy lib庫. 需提前安裝 `pip install numpy` 
import numpy as np 
def unique(data): 
 res = np.array(data) 
 return list(np.unique(res)) 
# test 
data = ['a', 'a', 1, 1, 2, 2, 'b', 'b', 2, 1] 
start_time = time.time() 
print("import numpy as np.unique:", unique(data)) 
print("time:" + str((time.time() - start_time) * 1000) + " ms")