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added new example

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KoustavCode 2020-09-30 23:28:02 +05:30
parent 27b66b4f31
commit 3709c10cd4

44
README.md vendored
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@ -59,6 +59,7 @@ So, here we go...
+ [ The disappearing variable from outer scope](#-the-disappearing-variable-from-outer-scope)
+ [ The mysterious key type conversion](#-the-mysterious-key-type-conversion)
+ [ Let's see if you can guess this?](#-lets-see-if-you-can-guess-this)
+ [ Copy DEEP without deep copy](#-copy-deep-without-deep-copy)
* [Section: Slippery Slopes](#section-slippery-slopes)
+ [ Modifying a dictionary while iterating over it](#-modifying-a-dictionary-while-iterating-over-it)
+ [ Stubborn `del` operation](#-stubborn-del-operation)
@ -1898,6 +1899,49 @@ a, b = a[b] = {}, 5
True
```
---
### ▶ Copy DEEP without deep copy
```py
>>> new_list = [1,2,4,5,6]
>>> new_list_copy = new_list
>>> new_list_copy.append(10)
```
**Output:**
```py
>>> new_list
[1, 2, 4, 5, 6, 10]
>>> new_list_copy
[1, 2, 4, 5, 6, 10]
```
***But....***
```py
>>> new_list = [1,2,4,5,6]
>>> new_list_dcopy = new_list[:]
>>> new_list_dcopy.append(20)
```
**Output:**
```py
>>> new_list
[1, 2, 4, 5, 6]
>>> new_list_dcopy
[1, 2, 4, 5, 6, 20]
```
_What did just happen then?_
#### 💡 Explanation:
In Python, we have concept of [deep copy](https://docs.python.org/3/library/copy.html) and [shallow copy](https://docs.python.org/3/library/copy.html).
In the first example, `new_list` is the original list and `new_list_copy` is the shallow copy of the original list. As a result changes made to the copied list has reflected back to the original list.
The second example shows that `new_list_dcopy` is a deep copy of the original list `new_list`, where changes made in the deep copied list doesn't reflect back to the original list.
One can easily deep copy a list without using the *copy.deepcopy(new_list)* just by using `slicing` , where any changes made to the copied list won't reflect back to the original list. Trick!!
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