Question

我有一个350MB的制表符分隔的文本文件。如果我尝试将其读入内存，则会出现内存不足异常。因此，我正在尝试遵循这些原则（即仅在几列中进行阅读）：

import pandas as pd

input_file_and_path = r'C:\Christian\ModellingData\X.txt'

column_names = [
    'X1'
    # , 'X2
]
raw_data = pd.DataFrame()
for chunk in pd.read_csv(input_file_and_path, names=column_names, chunksize=1000, sep='\t'):
    raw_data = pd.concat([raw_data, chunk], ignore_index=True)

print(raw_data.head())

不幸的是，我得到了：

Traceback (most recent call last):
  File "pandas\_libs\parsers.pyx", line 1134, in pandas._libs.parsers.TextReader._convert_tokens
  File "pandas\_libs\parsers.pyx", line 1240, in pandas._libs.parsers.TextReader._convert_with_dtype
  File "pandas\_libs\parsers.pyx", line 1256, in pandas._libs.parsers.TextReader._string_convert
  File "pandas\_libs\parsers.pyx", line 1494, in pandas._libs.parsers._string_box_utf8
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xae in position 5: invalid start byte

在处理上述异常期间，发生了另一个异常：

Traceback (most recent call last):
  File "C:/xxxx/EdaDataPrepRange1.py", line 17, in <module>
    for chunk in pd.read_csv(input_file_and_path, header=None, names=column_names, chunksize=1000, sep='\t'):
  File "C:\ProgramData\Anaconda3\lib\site-packages\pandas\io\parsers.py", line 1007, in __next__
    return self.get_chunk()
  File "C:\ProgramData\Anaconda3\lib\site-packages\pandas\io\parsers.py", line 1070, in get_chunk
    return self.read(nrows=size)
  File "C:\ProgramData\Anaconda3\lib\site-packages\pandas\io\parsers.py", line 1036, in read
    ret = self._engine.read(nrows)
  File "C:\ProgramData\Anaconda3\lib\site-packages\pandas\io\parsers.py", line 1848, in read
    data = self._reader.read(nrows)
  File "pandas\_libs\parsers.pyx", line 876, in pandas._libs.parsers.TextReader.read
  File "pandas\_libs\parsers.pyx", line 903, in pandas._libs.parsers.TextReader._read_low_memory
  File "pandas\_libs\parsers.pyx", line 968, in pandas._libs.parsers.TextReader._read_rows
  File "pandas\_libs\parsers.pyx", line 1094, in pandas._libs.parsers.TextReader._convert_column_data
  File "pandas\_libs\parsers.pyx", line 1141, in pandas._libs.parsers.TextReader._convert_tokens
  File "pandas\_libs\parsers.pyx", line 1240, in pandas._libs.parsers.TextReader._convert_with_dtype
  File "pandas\_libs\parsers.pyx", line 1256, in pandas._libs.parsers.TextReader._string_convert
  File "pandas\_libs\parsers.pyx", line 1494, in pandas._libs.parsers._string_box_utf8
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xae in position 5: invalid start byte

任何想法。顺便说一句，我通常如何处理大型文件并估算缺失的变量？最终，我需要阅读所有内容以确定例如要估算的中位数。

Answer 1

在使用encoding="utf-8"的同时使用pd.read_csv

他们在这里使用了这种编码。看看是否可行。 open(file path, encoding='windows-1252')：

参考：'utf-8' codec can't decode byte 0xa0 in position 4276: invalid start byte

工作解决方案

使用编码encoding="ISO-8859-1"

Answer 2

关于大文件问题，只需使用文件处理程序和上下文管理器即可：

with open("your_file.txt") as fileObject:
    for line in fileObject:
        do_something_with(line)

## No need to close file as 'with' automatically does that

这不会将整个文件加载到内存中。取而代之的是，它将一次加载一行，并且除非您存储引用，否则将“忘记”前几行。

另外，关于您的编码问题，只需在使用encoding="utf-8"时使用pd.read_csv。

大选项卡分隔文件中的异常读取已分块

2 个答案: