有没有办法在一行中执行以下操作？
[del item for item in new_json if item['Country'] in countries_to_remove]
上面给了我一个SyntaxError。
答案 0 :(得分：4)
del is a statement您无法使用as an expression in list comprehenstion。这就是为什么你得到java.lang.OutOfMemoryError: PermGen space
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:800)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at org.eclipse.jetty.webapp.WebAppClassLoader.loadClass(WebAppClassLoader.java:421)
at org.eclipse.jetty.webapp.WebAppClassLoader.loadClass(WebAppClassLoader.java:383)
at org.codehaus.jackson.map.ObjectMapper.<init>(ObjectMapper.java:390)
at org.codehaus.jackson.map.ObjectMapper.<init>(ObjectMapper.java:358)
at org.codehaus.jackson.map.ObjectMapper.<init>(ObjectMapper.java:328)
at org.apache.hadoop.hbase.client.Operation.<clinit>(Operation.java:40)
at org.apache.hadoop.hbase.client.MetaScanner.metaScan(MetaScanner.java:165)
at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.prefetchRegionCache(HConnectionManager.java:1158)
at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.locateRegionInMeta(HConnectionManager.java:1222)
at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.locateRegion(HConnectionManager.java:1110)
at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.locateRegion(HConnectionManager.java:1067)
at org.apache.hadoop.hbase.client.HTable.finishSetup(HTable.java:326)
at org.apache.hadoop.hbase.client.HTable.<init>(HTable.java:192)
at org.apache.hadoop.hbase.client.HTable.<init>(HTable.java:165)
at org.springframework.data.hadoop.hbase.HbaseUtils.getHTable(HbaseUtils.java:76)
at org.springframework.data.hadoop.hbase.HbaseTemplate.getTable(HbaseTemplate.java:75)
at org.springframework.data.hadoop.hbase.HbaseTemplate.execute(HbaseTemplate.java:54)
at org.springframework.data.hadoop.hbase.HbaseTemplate.get(HbaseTemplate.java:170)
at org.springframework.data.hadoop.hbase.HbaseTemplate.get(HbaseTemplate.java:160)
at edu.mayo.registry.fhir.rest.hbase.repository.HbaseRepository.partialScan(HbaseRepository.java:50)
at edu.mayo.registry.fhir.rest.controller.ESController.putIndexValue(ESController.java:61)
at edu.mayo.registry.fhir.rest.controller.ESController$$FastClassBySpringCGLIB$$729642a0.invoke(<generated>)
at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
。
您可以使用列表理解来创建新列表，而不包含您不想要的元素，例如
SyntaxError这实际上等同于
[item for item in new_json if item['Country'] not in countries_to_remove]
这种操作称为过滤列表，您可以使用内置result = []
for item in new_json:
if item['Country'] not in countries_to_remove:
result.append(item)
函数，如下所示
filter正如mgilson in the comments section所建议的那样，如果您只想改变原始列表，那么您可以使用切片赋值，就像这样
list(filter(lambda x: x['Country'] not in countries_to_remove, new_json))
答案 1 :(得分：4)
del是python中的一个语句，你不能在列表理解中有语句（你只能在那里有表达式）。为什么不将new_json创建为不包含要删除的项目的新列表或字典。示例=
new_json = [item for item in new_json if item['Country'] not in countries_to_remove]