如何根據語義相似性分割文字
取自 Greg Kamradt 精彩的筆記本：5_Levels_Of_Text_Splitting
所有功勞歸於他。
本指南涵蓋如何根據語義相似性分割區塊。如果嵌入向量相距足夠遠，則會分割區塊。
在高層次上，這會分割成句子，然後分組為 3 個句子的群組，然後合併嵌入空間中相似的句子。
安裝依賴項
!pip install --quiet langchain_experimental langchain_openai
載入範例資料
# This is a long document we can split up.
with open("state_of_the_union.txt") as f:
state_of_the_union = f.read()
建立文字分割器
若要實例化 SemanticChunker，我們必須指定一個嵌入模型。以下我們將使用 OpenAIEmbeddings。
from langchain_experimental.text_splitter import SemanticChunker
from langchain_openai.embeddings import OpenAIEmbeddings
text_splitter = SemanticChunker(OpenAIEmbeddings())
API 參考：SemanticChunker | OpenAIEmbeddings
分割文字
我們以通常的方式分割文字，例如，透過調用 .create_documents 來建立 LangChain Document 物件
docs = text_splitter.create_documents([state_of_the_union])
print(docs[0].page_content)
Madam Speaker, Madam Vice President, our First Lady and Second Gentleman. Members of Congress and the Cabinet. Justices of the Supreme Court. My fellow Americans. Last year COVID-19 kept us apart. This year we are finally together again. Tonight, we meet as Democrats Republicans and Independents. But most importantly as Americans. With a duty to one another to the American people to the Constitution. And with an unwavering resolve that freedom will always triumph over tyranny. Six days ago, Russia’s Vladimir Putin sought to shake the foundations of the free world thinking he could make it bend to his menacing ways. But he badly miscalculated. He thought he could roll into Ukraine and the world would roll over. Instead he met a wall of strength he never imagined. He met the Ukrainian people. From President Zelenskyy to every Ukrainian, their fearlessness, their courage, their determination, inspires the world. Groups of citizens blocking tanks with their bodies. Everyone from students to retirees teachers turned soldiers defending their homeland. In this struggle as President Zelenskyy said in his speech to the European Parliament “Light will win over darkness.” The Ukrainian Ambassador to the United States is here tonight. Let each of us here tonight in this Chamber send an unmistakable signal to Ukraine and to the world. Please rise if you are able and show that, Yes, we the United States of America stand with the Ukrainian people. Throughout our history we’ve learned this lesson when dictators do not pay a price for their aggression they cause more chaos. They keep moving.
斷點
此區塊器的工作原理是確定何時「斷開」句子。這是透過尋找任意兩個句子之間嵌入向量的差異來完成的。當差異超過某個閾值時，就會分割它們。
有幾種方法可以確定閾值是多少，這些方法由 breakpoint_threshold_type kwarg 控制。
注意：如果產生的區塊大小太小/太大，可以使用額外的 kwargs breakpoint_threshold_amount 和 min_chunk_size 進行調整。
百分位數
預設的分割方式是基於百分位數。在此方法中，計算所有句子之間的差異，然後分割任何大於 X 百分位數的差異。X 的預設值為 95.0，可以透過關鍵字參數 breakpoint_threshold_amount 進行調整，該參數預期為介於 0.0 和 100.0 之間的數字。
text_splitter = SemanticChunker(
OpenAIEmbeddings(), breakpoint_threshold_type="percentile"
)
docs = text_splitter.create_documents([state_of_the_union])
print(docs[0].page_content)
Madam Speaker, Madam Vice President, our First Lady and Second Gentleman. Members of Congress and the Cabinet. Justices of the Supreme Court. My fellow Americans. Last year COVID-19 kept us apart. This year we are finally together again. Tonight, we meet as Democrats Republicans and Independents. But most importantly as Americans. With a duty to one another to the American people to the Constitution. And with an unwavering resolve that freedom will always triumph over tyranny. Six days ago, Russia’s Vladimir Putin sought to shake the foundations of the free world thinking he could make it bend to his menacing ways. But he badly miscalculated. He thought he could roll into Ukraine and the world would roll over. Instead he met a wall of strength he never imagined. He met the Ukrainian people. From President Zelenskyy to every Ukrainian, their fearlessness, their courage, their determination, inspires the world. Groups of citizens blocking tanks with their bodies. Everyone from students to retirees teachers turned soldiers defending their homeland. In this struggle as President Zelenskyy said in his speech to the European Parliament “Light will win over darkness.” The Ukrainian Ambassador to the United States is here tonight. Let each of us here tonight in this Chamber send an unmistakable signal to Ukraine and to the world. Please rise if you are able and show that, Yes, we the United States of America stand with the Ukrainian people. Throughout our history we’ve learned this lesson when dictators do not pay a price for their aggression they cause more chaos. They keep moving.
print(len(docs))
26
標準差
在此方法中，任何大於 X 個標準差的差異都會被分割。X 的預設值為 3.0，可以透過關鍵字參數 breakpoint_threshold_amount 進行調整。
text_splitter = SemanticChunker(
OpenAIEmbeddings(), breakpoint_threshold_type="standard_deviation"
)
docs = text_splitter.create_documents([state_of_the_union])
print(docs[0].page_content)
Madam Speaker, Madam Vice President, our First Lady and Second Gentleman. Members of Congress and the Cabinet. Justices of the Supreme Court. My fellow Americans. Last year COVID-19 kept us apart. This year we are finally together again. Tonight, we meet as Democrats Republicans and Independents. But most importantly as Americans. With a duty to one another to the American people to the Constitution. And with an unwavering resolve that freedom will always triumph over tyranny. Six days ago, Russia’s Vladimir Putin sought to shake the foundations of the free world thinking he could make it bend to his menacing ways. But he badly miscalculated. He thought he could roll into Ukraine and the world would roll over. Instead he met a wall of strength he never imagined. He met the Ukrainian people. From President Zelenskyy to every Ukrainian, their fearlessness, their courage, their determination, inspires the world. Groups of citizens blocking tanks with their bodies. Everyone from students to retirees teachers turned soldiers defending their homeland. In this struggle as President Zelenskyy said in his speech to the European Parliament “Light will win over darkness.” The Ukrainian Ambassador to the United States is here tonight. Let each of us here tonight in this Chamber send an unmistakable signal to Ukraine and to the world. Please rise if you are able and show that, Yes, we the United States of America stand with the Ukrainian people. Throughout our history we’ve learned this lesson when dictators do not pay a price for their aggression they cause more chaos. They keep moving. And the costs and the threats to America and the world keep rising. That’s why the NATO Alliance was created to secure peace and stability in Europe after World War 2. The United States is a member along with 29 other nations. It matters. American diplomacy matters. American resolve matters. Putin’s latest attack on Ukraine was premeditated and unprovoked. He rejected repeated efforts at diplomacy. He thought the West and NATO wouldn’t respond. And he thought he could divide us at home. Putin was wrong. We were ready. Here is what we did. We prepared extensively and carefully. We spent months building a coalition of other freedom-loving nations from Europe and the Americas to Asia and Africa to confront Putin. I spent countless hours unifying our European allies. We shared with the world in advance what we knew Putin was planning and precisely how he would try to falsely justify his aggression. We countered Russia’s lies with truth. And now that he has acted the free world is holding him accountable. Along with twenty-seven members of the European Union including France, Germany, Italy, as well as countries like the United Kingdom, Canada, Japan, Korea, Australia, New Zealand, and many others, even Switzerland. We are inflicting pain on Russia and supporting the people of Ukraine. Putin is now isolated from the world more than ever. Together with our allies –we are right now enforcing powerful economic sanctions. We are cutting off Russia’s largest banks from the international financial system. Preventing Russia’s central bank from defending the Russian Ruble making Putin’s $630 Billion “war fund” worthless. We are choking off Russia’s access to technology that will sap its economic strength and weaken its military for years to come. Tonight I say to the Russian oligarchs and corrupt leaders who have bilked billions of dollars off this violent regime no more. The U.S. Department of Justice is assembling a dedicated task force to go after the crimes of Russian oligarchs. We are joining with our European allies to find and seize your yachts your luxury apartments your private jets. We are coming for your ill-begotten gains. And tonight I am announcing that we will join our allies in closing off American air space to all Russian flights – further isolating Russia – and adding an additional squeeze –on their economy. The Ruble has lost 30% of its value. The Russian stock market has lost 40% of its value and trading remains suspended. Russia’s economy is reeling and Putin alone is to blame. Together with our allies we are providing support to the Ukrainians in their fight for freedom. Military assistance. Economic assistance. Humanitarian assistance. We are giving more than $1 Billion in direct assistance to Ukraine. And we will continue to aid the Ukrainian people as they defend their country and to help ease their suffering. Let me be clear, our forces are not engaged and will not engage in conflict with Russian forces in Ukraine. Our forces are not going to Europe to fight in Ukraine, but to defend our NATO Allies – in the event that Putin decides to keep moving west. For that purpose we’ve mobilized American ground forces, air squadrons, and ship deployments to protect NATO countries including Poland, Romania, Latvia, Lithuania, and Estonia. As I have made crystal clear the United States and our Allies will defend every inch of territory of NATO countries with the full force of our collective power. And we remain clear-eyed. The Ukrainians are fighting back with pure courage. But the next few days weeks, months, will be hard on them. Putin has unleashed violence and chaos. But while he may make gains on the battlefield – he will pay a continuing high price over the long run. And a proud Ukrainian people, who have known 30 years of independence, have repeatedly shown that they will not tolerate anyone who tries to take their country backwards. To all Americans, I will be honest with you, as I’ve always promised. A Russian dictator, invading a foreign country, has costs around the world. And I’m taking robust action to make sure the pain of our sanctions is targeted at Russia’s economy. And I will use every tool at our disposal to protect American businesses and consumers. Tonight, I can announce that the United States has worked with 30 other countries to release 60 Million barrels of oil from reserves around the world. America will lead that effort, releasing 30 Million barrels from our own Strategic Petroleum Reserve. And we stand ready to do more if necessary, unified with our allies. These steps will help blunt gas prices here at home. And I know the news about what’s happening can seem alarming.
print(len(docs))
4
四分位距
在此方法中，四分位距用於分割區塊。四分位距可以透過關鍵字參數 breakpoint_threshold_amount 進行縮放，預設值為 1.5。
text_splitter = SemanticChunker(
OpenAIEmbeddings(), breakpoint_threshold_type="interquartile"
)
docs = text_splitter.create_documents([state_of_the_union])
print(docs[0].page_content)
Madam Speaker, Madam Vice President, our First Lady and Second Gentleman. Members of Congress and the Cabinet. Justices of the Supreme Court. My fellow Americans. Last year COVID-19 kept us apart. This year we are finally together again. Tonight, we meet as Democrats Republicans and Independents. But most importantly as Americans. With a duty to one another to the American people to the Constitution. And with an unwavering resolve that freedom will always triumph over tyranny. Six days ago, Russia’s Vladimir Putin sought to shake the foundations of the free world thinking he could make it bend to his menacing ways. But he badly miscalculated. He thought he could roll into Ukraine and the world would roll over. Instead he met a wall of strength he never imagined. He met the Ukrainian people. From President Zelenskyy to every Ukrainian, their fearlessness, their courage, their determination, inspires the world. Groups of citizens blocking tanks with their bodies. Everyone from students to retirees teachers turned soldiers defending their homeland. In this struggle as President Zelenskyy said in his speech to the European Parliament “Light will win over darkness.” The Ukrainian Ambassador to the United States is here tonight. Let each of us here tonight in this Chamber send an unmistakable signal to Ukraine and to the world. Please rise if you are able and show that, Yes, we the United States of America stand with the Ukrainian people. Throughout our history we’ve learned this lesson when dictators do not pay a price for their aggression they cause more chaos. They keep moving.
print(len(docs))
25
梯度
在此方法中，距離梯度與百分位數方法一起用於分割區塊。當區塊彼此高度相關或特定於某個領域（例如法律或醫療）時，此方法很有用。其想法是對梯度陣列應用異常偵測，以便分佈變得更寬，並且更容易識別高度語義資料中的邊界。與百分位數方法類似，分割可以透過關鍵字參數 breakpoint_threshold_amount 進行調整，該參數預期為介於 0.0 和 100.0 之間的數字，預設值為 95.0。
text_splitter = SemanticChunker(
OpenAIEmbeddings(), breakpoint_threshold_type="gradient"
)
docs = text_splitter.create_documents([state_of_the_union])
print(docs[0].page_content)
Madam Speaker, Madam Vice President, our First Lady and Second Gentleman.
print(len(docs))
26