python - 根据数量为每个类别选择 1 行

Question

我有 5 列的列表，其中第 5 列是数字列表，第 1 列是组标识符。总共有 500 行，但只有 24 组。

我想要的是从每个组标识符中仅选择第 5 列中数字最小的一行。

例如

sheet= """ 
cmn1\tcmn2\tcmn3\tcmn4\tcmn5
rob\t45\tfoo\tbar\t0.0001
Steve\t32\tfoo\tspam\t0.01
rob\t45\tbar\tfoo\t0.0000001
Steve\t32\tfoo\tbar\t0.1"""

这是期望的结果:

cmn1\tcmn2\tcmn3\tcmn4\tcmn5
Steve\t32\tfoo\tspam\t.01
rob\t45\tbar\tfoo\t0.0000001

我在每行列表中都有我的字段，但我不知道如何选择零件[4]中编号最小的行

for line in sheet:
     line = sheet.strip().split("\n")

parts = []

for part in line: 
      parts = []
      parts = part.split("\t")
      print parts [0], parts [1], parts[2], parts[3], parts[4]

Answer 1

sheet= """ cmn1 cmn2 cmn3 cmn4 cmn5
rob  45   foo  bar  0.0001
Steve 32  foo  spam 0.01
rob   45  bar  foo  0.0000001
Steve 32  foo  bar  0.1"""

from collections import defaultdict

d = defaultdict(list)
spl = sheet.splitlines()
header = spl[0]
# iterate over all lines except header
for line in spl[1:]:
    # split once on whitespace using name as the key 
    name = line.split(None,1)[0]
    # append each line to our list of values
    d[name].append(line)

# get min of each line in our values based on the last float value
for v in d.values():
    print(min(v,key=lambda x: float(x.split()[-1])))

Steve 32  foo  spam 0.01
rob   45  bar  foo  0.0000001

如果订单很重要，您可以使用 OrderedDict 广告，并且还会随时检查:

from collections import OrderedDict

d = OrderedDict()
spl = sheet.splitlines()
header = spl[0]
for line in spl[1:]:
    # unpack five elements after splitting
    # using name as key and f to cast to float and compare
    name, _, _, _, f = line.split()
    # if key exists compare float value to current float value
    # keeping or replacing the values based on the outcome
    if name in d and float(d[name].split()[-1]) > float(f):
        d[name] = line
    # else if first time seeing name just add it
    elif name not in d:
        d[name] = line

print(header)
for v in d.values():
    print(v)

cmn1 cmn2 cmn3 cmn4 cmn5
rob   45  bar  foo  0.0000001
Steve 32  foo  spam 0.01

使用您编辑的行，您可以看到输出没有改变，它将与原来完全相同:

for v in d.values():
    print(repr(v))

'rob\t45\tbar\tfoo\t0.0000001'
'Steve\t32\tfoo\tspam\t0.01