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Add new example: Deep Down, we're all the same

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Satwik Kansal 2018-01-07 11:57:50 +05:30
parent 78a1218dbd
commit 118f51d042

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README.md vendored
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@ -1736,6 +1736,52 @@ Why did `Yo()._Yo__honey` worked? Only Indian readers would understand.
--- ---
### Deep down, we're all the same.
Suggested by @Lucas-C in [this](https://github.com/satwikkansal/wtfpython/issues/36) issue.
```py
class WTF:
pass
```
**Output:**
```py
>>> WTF() == WTF() # two different instances can't be equal
False
>>> WTF() is WTF() # identities are also different
False
>>> hash(WTF()) == hash(WTF()) # hashes _should_ be different as well
True
>>> id(WTF()) == id(WTF())
True
```
#### 💡 Explanation:
* When `id` was called, Python created a `WTF` class object and passed it to the `id` function. The `id` function takes its `id` (its memory location), and throws away the object. The object is destroyed.
* When we do this twice in succession, Python allocates the same memory location to this second object as well. Since (in CPython) `id` uses the memory location as the object id, the id of the two objects is the same.
* So, object's id is only unique for the lifetime of the object. After the object is destroyed, or before it is created, something else can have the same id.
* But why did the `is` operator evaluated to `False`? Let's see with this snippet.
```py
class WTF(object):
def __init__(self): print("I ")
def __del__(self): print("D ")
```
**Output:**
```py
>>> WTF() is WTF()
I I D D
>>> id(WTF()) == id(WTF())
I D I D
```
As you may observe, the order in which the objects are destroyed is what made all the difference here.
---
### Let's see if you can guess this? ### Let's see if you can guess this?
Suggested by @PiaFraus in [this](https://github.com/satwikkansal/wtfPython/issues/9) issue. Suggested by @PiaFraus in [this](https://github.com/satwikkansal/wtfPython/issues/9) issue.