如何在Python中读取块数据？

Question

我在读取数据文件时遇到了问题：

///
* ABC Names
A-06,B-18,
* Data
 1.727e-01, 1.258e-01, 2.724e-01, 2.599e-01,-3.266e-01,-9.425e-02,-6.213e-02, 1.479e-01,
 1.219e-01, 1.174e-01, 2.213e-01, 2.875e-01,-2.306e-01,-3.900e-03,-5.269e-02, 7.420e-02,
 2.592e-01, 2.513e-01, 2.242e-01, 2.620e-01,-1.346e-01,-6.844e-02,-4.139e-02, 9.502e-02,
 1.981e-01, 1.937e-01, 2.336e-01, 1.617e-01,-4.240e-02, 2.285e-02, 1.878e-02, 1.064e-01,
 9.562e-02, 6.727e-02, 1.135e-01, 6.765e-02,-7.850e-02, 6.711e-02, 1.317e-02, 8.367e-02, 
* Starting position
     -.5000E+01
///

这个代码是在Python中运行的吗？我试过用 readline() 和 readlines() 这两个函数，但没有得到结果。

Answer 1

假设文件名是“abc.txt”，并且它在当前目录下；那么下面这个Python脚本：

f = open("abc.txt")
all_lines = f.readlines()

会把文件里的所有行读取到一个字符串列表 all_lines 中，每一行的结尾都会有 \n。

至于你接下来想要做什么，我们无法猜测，除非你告诉我们。不过你问的那部分，关于读取文件的内容，应该是没问题的。

Answer 2

这个方法应该适用于名字为 'a'、'b' 和 'c' 的文件。它会创建一个字典，字典里的键就是这些块的标题，像这样：

{'a':['line1','line2'],'b':['line1'],'c':['line1','line2','line3']} 

代码：

block_names = ['b','a','c']

for line in open('file.txt'):
    block_dict = {}  #dict to populate with lists of lines
    block = []  # dummy block in case there is data or lines before first block
    ck_nm = [blk_nm for blk_nm in block_names if line.startswith(blk_nm)]  #search block names for a match
    if ck_nm: # did we find a match?
        block_dict[ck_nm[0]] = block = []  # set current block
    else:
        block.append(line)  #..or line.split(',') ..however you want to parse the data

Answer 3

这里有一段代码的猜测，它可能会加载这个文件的类型，这段代码应该是比较稳健的：

f = open("mdata.txt")

data_dict = {}
section = None
data_for_section = ""
for line in f:
    line = line.strip() #remove whitespace at start and end

    if section != None and (line[0] == "*" or line == "///"):
        # if we've just finished a section, put whatever we got into the data dict
        data_dict[section] = [bit for bit in data_for_section.split(",") if bit != ""]

    if line[0] == "*":
        # "*" denotes the start of a new section, probably, so remember the name
        section = line [2:]
        data_for_section = ""
        continue
    data_for_section += line

f.close()
#got the data, now for some output
print "loaded file. Found headings: %s"%(", ".join(data_dict.keys()))

for key in data_dict.keys():
    if len(data_dict[key])>5:
        print key, ": array of %i entries"%len(data_dict[key])
    else:
        print key, ": ", data_dict[key]

这段代码会输出你文件中的内容：

loaded file. Found headings: ABC Names, Data, Starting position
ABC Names :  ['A-06', 'B-18']
Data : array of 40 entries
Starting position :  ['-.5000E+01']

当然，如果是数据和起始位置的话，你可能想把数据字符串的列表转换成浮点数：

startingPosition = float(data_dict["Starting position"][0])
data_list_of_floats = map(float, data_dict["Data"])

至于ABC名称以及它们如何与文件的其他部分结合，我们还需要更多的信息。