Python - 处理非结构化数据

已经以行和列格式存在的数据或可以轻松转换为行和列以便以后可以很好地放入数据库的数据称为结构化数据。例如 CSV、TXT、XLS 文件等。这些文件具有分隔符和固定或可变宽度，其中缺失值表示为分隔符之间的空格。但有时我们得到的数据行不是固定宽度，或者它们只是 HTML、图像或 pdf 文件。此类数据称为非结构化数据。虽然可以通过处理 HTML 标签来处理 HTML 文件，但 Twitter 的提要或新闻提要中的纯文本文档如果没有分隔符，则没有标签可处理。在这种情况下，我们使用来自各种 Python 库的不同内置函数来处理文件。

读取数据

在下面的例子中，我们获取一个文本文件并读取文件，并分隔其中的每一行。接下来我们可以将输出进一步划分为行和单词。原始文件是一个文本文件，其中包含一些描述 Python 语言的段落。

filename = 'path\input.txt'  

with open(filename) as fn:  

# Read each line
   ln = fn.readline()

# Keep count of lines
   lncnt = 1
   while ln:
       print("Line {}: {}".format(lncnt, ln.strip()))
       ln = fn.readline()
       lncnt += 1

当我们执行上述代码时，它会产生以下结果。

Line 1: Python is an interpreted high-level programming language for general-purpose programming. Created by Guido van Rossum and first released in 1991, Python has a design philosophy that emphasizes code readability, notably using significant whitespace. It provides constructs that enable clear programming on both small and large scales.
Line 2: Python features a dynamic type system and automatic memory management. It supports multiple programming paradigms, including object-oriented, imperative, functional and procedural, and has a large and comprehensive standard library.
Line 3: Python interpreters are available for many operating systems. CPython, the reference implementation of Python, is open source software and has a community-based development model, as do nearly all of its variant implementations. CPython is managed by the non-profit Python Software Foundation.

计算词频

我们可以使用计数器函数计算文件中单词的频率，如下所示。

from collections import Counter

with open(r'pathinput2.txt') as f:
               p = Counter(f.read().split())
               print(p)

当我们执行上述代码时，它会产生以下结果。

Counter({'and': 3, 'Python': 3, 'that': 2, 'a': 2, 'programming': 2, 'code': 1, '1991,': 1, 'is': 1, 'programming.': 1, 'dynamic': 1, 'an': 1, 'design': 1, 'in': 1, 'high-level': 1, 'management.': 1, 'features': 1, 'readability,': 1, 'van': 1, 'both': 1, 'for': 1, 'Rossum': 1, 'system': 1, 'provides': 1, 'memory': 1, 'has': 1, 'type': 1, 'enable': 1, 'Created': 1, 'philosophy': 1, 'constructs': 1, 'emphasizes': 1, 'general-purpose': 1, 'notably': 1, 'released': 1, 'significant': 1, 'Guido': 1, 'using': 1, 'interpreted': 1, 'by': 1, 'on': 1, 'language': 1, 'whitespace.': 1, 'clear': 1, 'It': 1, 'large': 1, 'small': 1, 'automatic': 1, 'scales.': 1, 'first': 1})