[英]python compare two lists and replace original list if there is a match
I have two lists containing strings.我有两个包含字符串的列表。 I want to take each item in the base_list
and search to see if there is a match for the first 3 characters in any values from the custom list
.我想获取base_list
每个项目并搜索以查看custom list
中任何值中的前 3 个字符是否匹配。 If there is a match, replace the original value in base_list
with the one from custom_list
.如果有匹配,替换原来的值base_list
从一个custom_list
。 If there is no match, keep the original value.如果不匹配,则保留原始值。
base_list = ["abc123", "cde123", "efg456", "ghi123"]
custom_list = ["abc321", "efg654"]
Desired Output:期望输出:
modified_base_list = ["abc321", "cde123", "efg654", "ghi123"]
Eventually I also want to write this new modified_base_list
as a file containing the items, one per line.最后,我还想将这个新的modified_base_list
写成一个包含项目的文件,每行一个。
I've tried:我试过了:
modified_base_list = []
for custom in custom_list:
for base in base_list:
if custom[:3] == base[:3]:
modified_base_list.append(custom)
else:
modified_base_list.append(base)
print(modified_base_list)
with open('newfile.txt', 'w') as f:
for s in modified_base_list:
f.write(s)
***EDITING QUESTION to account for lists that have 15k+ lines to find a faster way to do this. ***编辑问题以解决具有 15k+ 行的列表以找到执行此操作的更快方法。
This is a solution that mutates the original list, replacing only those where the desired match exists:这是一种改变原始列表的解决方案,仅替换存在所需匹配项的列表:
>>> base_list = ["abc123", "cde123", "efg456", "ghi123"]
>>> custom_list = ["abc321", "efg654"]
>>> for i, x in enumerate(base_list):
for test in custom_list:
if test[:3] == x[:3]:
base_list[i] = test
break
>>> base_list
['abc321', 'cde123', 'efg654', 'ghi123']
Of course if you don't want to modify the original list, you can create a coopy of it first using modified_base_list = base_list[:]
.当然,如果您不想修改原始列表,您可以先使用modified_base_list = base_list[:]
创建一个副本。
You can also follow your own idea but in that case, you have to make sure that you are primarily iterating over base_list
and won't add items multiple times:您也可以遵循自己的想法,但在这种情况下,您必须确保主要迭代base_list
并且不会多次添加项目:
modified_base_list = []
for base in base_list:
found = False
for custom in custom_list:
if custom[:3] == base[:3]:
modified_base_list.append(custom)
found = True
break
if not found:
modified_base_list.append(base)
You can also use for…else
here instead of that utility variable found
:您也可以在此处使用for…else
而不是found
实用程序变量:
for base in base_list:
for custom in custom_list:
if custom[:3] == base[:3]:
modified_base_list.append(custom)
break
else:
modified_base_list.append(base)
You could use a list comprehension containing a generator expression:您可以使用包含生成器表达式的列表推导式:
base_list = ["abc123", "cde123", "efg456", "ghi123"]
custom_list = ["abc321", "efg654"]
modified_base_list = [next((y for y in custom_list if y[:3] == x[:3]), x) for x in base_list]
# ['abc321', 'cde123', 'efg654', 'ghi123']
Note that I'm assuming if the same 3 character prefix occurs multiple times in custom_list
that you only wish to take the first instance.请注意,我假设如果相同的 3 个字符前缀在custom_list
中多次custom_list
,您只希望采用第一个实例。
You can use a combination of list comprehension
and map
for this:为此,您可以结合使用list comprehension
和map
:
base_list = ["abc123", "cde123", "efg456", "ghi123"]
custom_list = ["abc321", "efg654"]
smaller_custom = [y[:3] for y in custom_list]
modified_base_list = ["**{}**".format(custom_list[smaller_custom.index(x[:3])]) if x[:3] in smaller_custom else x for x in base_list]
# ['**abc321**', 'cde123', '**efg654**', 'ghi123']
with open('output_data.txt','w') as outfile:
outfile.write("\n".join(modified_base_list))
I hope this helps.我希望这有帮助。
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