如何檢查字符串是否以負數和浮點數開頭？ [蟒蛇]

Question

我有一段代碼看起來像這樣：

    loc2 = {}
    with open('loc.txt') as filename:
    for line in filename:
        a = line.strip()
        if a.replace('.','',1).isdigit():
            loc2[float(a[0])] = a[1:]
    return loc2

在其中，我需要檢查一個數字是否可以為負數，整數或浮點數（該數字始終位於文件loc.txt中的行首，並且始終位於整行中），然后將其添加到字典作為關鍵。 有人可以幫我嗎？ 不知道如何解決這個問題。 我試圖替換“。” 帶有空白空間，但這顯然行不通，也無法解決我的負數問題。 我還是python的菜鳥。 謝謝！

loc.txt的示例：

1
stuff
1.1
stuff
-4
stuff

東西是東西，以后會作為值添加到字典中。

Answer 1

您可以嘗試使用try else語句。

loc2 = {}
with open('loc.txt') as filename:
    for i,line in enumerate(filename):
        # split the given line up by space into a list
        a = line.strip().split()
        try:
            # attempt to convert first part of line into float
            k = float(a[0])
            # assignment that key the value of the rest of the string
            loc2[k] = ' '.join(a[1:])
        except ValueError as ex:
            # actions performed when the line does not start with number
            print('Line %d did not start with a number.'%i)
        else:
            # actions performed when the float conversion was successful
            print('Key {} has been added with value: {}'.format(k,loc2[k]))

loc.txt文件：

-1 one
0 two
1.5 three
-5.708 four
test

輸出繼電器：

Key -1.0 has been added with value: one
Key 0.0 has been added with value: two
Key 1.5 has been added with value: three
Key -5.708 has been added with value: four
Line 4 did not start with a number.

loc2內容

{-1.0: 'one', 0.0: 'two', 1.5: 'three', -5.708: 'four'}