Python 实用宝典

Question 1

I would like to get just the folder path from the full path to a file.

For example T:\Data\DBDesign\DBDesign_93_v141b.mdb and I would like to get just T:\Data\DBDesign (excluding the \DBDesign_93_v141b.mdb).

I have tried something like this:

existGDBPath = r'T:\Data\DBDesign\DBDesign_93_v141b.mdb'
wkspFldr = str(existGDBPath.split('\\')[0:-1])
print wkspFldr

but it gave me a result like this:

['T:', 'Data', 'DBDesign']

which is not the result that I require (being T:\Data\DBDesign).

Any ideas on how I can get the path to my file?

Question 2

You were almost there with your use of the split function. You just needed to join the strings, like follows.

>>> import os
>>> '\\'.join(existGDBPath.split('\\')[0:-1])
'T:\\Data\\DBDesign'

Although, I would recommend using the os.path.dirname function to do this, you just need to pass the string, and it’ll do the work for you. Since, you seem to be on windows, consider using the abspath function too. An example:

>>> import os
>>> os.path.dirname(os.path.abspath(existGDBPath))
'T:\\Data\\DBDesign'

If you want both the file name and the directory path after being split, you can use the os.path.split function which returns a tuple, as follows.

>>> import os
>>> os.path.split(os.path.abspath(existGDBPath))
('T:\\Data\\DBDesign', 'DBDesign_93_v141b.mdb')

Question 3

WITH PATHLIB MODULE (UPDATED ANSWER)

One should consider using pathlib for new development. It is in the stdlib for Python3.4, but available on PyPI for earlier versions. This library provides a more object-orented method to manipulate paths <opinion> and is much easier read and program with </opinion>.

>>> import pathlib
>>> existGDBPath = pathlib.Path(r'T:\Data\DBDesign\DBDesign_93_v141b.mdb')
>>> wkspFldr = existGDBPath.parent
>>> print wkspFldr
Path('T:\Data\DBDesign')

WITH OS MODULE

Use the os.path module:

>>> import os
>>> existGDBPath = r'T:\Data\DBDesign\DBDesign_93_v141b.mdb'
>>> wkspFldr = os.path.dirname(existGDBPath)
>>> print wkspFldr 
'T:\Data\DBDesign'

You can go ahead and assume that if you need to do some sort of filename manipulation it’s already been implemented in os.path. If not, you’ll still probably need to use this module as the building block.

Question 4

The built-in submodule os.path has a function for that very task.

import os
os.path.dirname('T:\Data\DBDesign\DBDesign_93_v141b.mdb')

Question 5

Here is the code:

import os
existGDBPath = r'T:\Data\DBDesign\DBDesign_93_v141b.mdb'
wkspFldr = os.path.dirname(existGDBPath)
print wkspFldr # T:\Data\DBDesign

Question 6

Here is my little utility helper for splitting paths int file, path tokens:

import os    
# usage: file, path = splitPath(s)
def splitPath(s):
    f = os.path.basename(s)
    p = s[:-(len(f))-1]
    return f, p

Question 7

Anyone trying to do this in the ESRI GIS Table field calculator interface can do this with the Python parser:

PathToContainingFolder =

"\\".join(!FullFilePathWithFileName!.split("\\")[0:-1])

so that

\Users\me\Desktop\New folder\file.txt

becomes

\Users\me\Desktop\New folder

Question 8

我有字典d = {1:-0.3246, 2:-0.9185, 3:-3985, ...}。

如何将的所有值提取d到列表中l？

Question 9

I have a dictionary d = {1:-0.3246, 2:-0.9185, 3:-3985, ...}.

How do I extract all of the values of d into a list l?

Question 10

如果你只需要字典的键1，2和3使用：your_dict.keys()。

如果你只需要在字典中的值-0.3246，-0.9185和-3985使用：your_dict.values()。

如果您想同时使用键和值，请使用：your_dict.items()返回一个元组列表[(key1, value1), (key2, value2), ...]。

Question 11

If you only need the dictionary keys 1, 2, and 3 use: your_dict.keys().

If you only need the dictionary values -0.3246, -0.9185, and -3985 use: your_dict.values().

If you want both keys and values use: your_dict.items() which returns a list of tuples [(key1, value1), (key2, value2), ...].

Question 12

使用 values()

>>> d = {1:-0.3246, 2:-0.9185, 3:-3985}

>>> d.values()
<<< [-0.3246, -0.9185, -3985]

Question 13

Use values()

>>> d = {1:-0.3246, 2:-0.9185, 3:-3985}

>>> d.values()
<<< [-0.3246, -0.9185, -3985]

Question 14

如果需要所有值，请使用以下命令：

dict_name_goes_here.values()

如果需要所有键，请使用以下命令：

dict_name_goes_here.keys()

如果您想要所有项目（键和值），则可以使用以下命令：

dict_name_goes_here.items()

Question 15

If you want all of the values, use this:

dict_name_goes_here.values()

If you want all of the keys, use this:

dict_name_goes_here.keys()

IF you want all of the items (both keys and values), I would use this:

dict_name_goes_here.items()

Question 16

values()在dict上调用方法。

Question 17

Call the values() method on the dict.

Question 18

对于Python 3，您需要：

list_of_dict_values = list(dict_name.values())

Question 19

For Python 3, you need:

list_of_dict_values = list(dict_name.values())

Question 20

对于嵌套字典，字典列表和列出字典的字典，…您可以使用

def get_all_values(d):
    if isinstance(d, dict):
        for v in d.values():
            yield from get_all_values(v)
    elif isinstance(d, list):
        for v in d:
            yield from get_all_values(v)
    else:
        yield d

一个例子：

d = {'a': 1, 'b': {'c': 2, 'd': [3, 4]}, 'e': [{'f': 5}, {'g': 6}]}

list(get_all_values(d)) # returns [1, 2, 3, 4, 5, 6]

PS：我爱yield。;-)

Question 21

For nested dicts, lists of dicts, and dicts of listed dicts, … you can use

def get_all_values(d):
    if isinstance(d, dict):
        for v in d.values():
            yield from get_all_values(v)
    elif isinstance(d, list):
        for v in d:
            yield from get_all_values(v)
    else:
        yield d

An example:

d = {'a': 1, 'b': {'c': 2, 'd': [3, 4]}, 'e': [{'f': 5}, {'g': 6}]}

list(get_all_values(d)) # returns [1, 2, 3, 4, 5, 6]

PS: I love yield. ;-)

Question 22

如果需要所有值，请使用以下命令：

dict_name_goes_here.values()

Question 23

If you want all of the values, use this:

dict_name_goes_here.values()

Question 24

d = <dict>
values = d.values()

Question 25

d = <dict>
values = d.values()

Question 26

要查看按键：

for key in d.keys():
    print(key)

要获取每个键所引用的值：

for key in d.keys():
    print(d[key])

添加到列表：

for key in d.keys():
    mylist.append(d[key])

Question 27

To see the keys:

for key in d.keys():
    print(key)

To get the values that each key is referencing:

for key in d.keys():
    print(d[key])

Add to a list:

for key in d.keys():
    mylist.append(d[key])

Question 28

Python的鸭式输入原则上应确定对象可以执行的操作，即其属性和方法。通过查看字典对象，可以尝试猜测它是否具有以下至少一项：dict.keys()或dict.values()方法。您应该尝试将这种方法用于将来在运行时会进行类型检查的编程语言，尤其是具有鸭式语言的语言。

Question 29

Pythonic duck-typing should in principle determine what an object can do, i.e., its properties and methods. By looking at a dictionary object one may try to guess it has at least one of the following: dict.keys() or dict.values() methods. You should try to use this approach for future work with programming languages whose type checking occurs at runtime, especially those with the duck-typing nature.

Question 30

dictionary_name={key1:value1,key2:value2,key3:value3}
dictionary_name.values()

Question 31

dictionary_name={key1:value1,key2:value2,key3:value3}
dictionary_name.values()

Python 实用宝典

标签归档：extract

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