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Add new example: Wild imports
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README.md
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README.md
vendored
@ -1858,21 +1858,22 @@ print(x, ': x in global')
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```
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3\.
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```
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x = 1
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print([x for x in range(5)])
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print(x, ': x in global')
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```
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**Output (on Python 2.x):**
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**Output (Python 2.x):**
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```
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>>> x = 1
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>>> print([x for x in range(5)])
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[0, 1, 2, 3, 4]
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>>> print(x, ': x in global')
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(4, ': x in global')
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```
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**Output (on Python 3.x):**
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**Output (Python 3.x):**
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```
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>>> x = 1
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>>> print([x for x in range(5)])
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[0, 1, 2, 3, 4]
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>>> print(x, ': x in global')
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1 : x in global
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```
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@ -2185,12 +2186,10 @@ class SomeClass:
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- A generator expression has its own scope.
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- Starting from Python 3.X, list comprehensions also have their own scope.
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---
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---
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### ▶ Needles in a Haystack
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### ▶ Needles in a Haystack ^
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1\.
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```py
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@ -2229,7 +2228,31 @@ e
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tuple()
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```
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3\. Not asserting strongly enough
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3\.
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```
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ten_words_list = [
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"some",
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"very",
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"big",
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"list",
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"that"
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"consists",
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"of",
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"exactly",
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"ten",
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"words"
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]
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```
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**Output**
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```py
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>>> len(ten_words_list)
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9
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```
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4\. Not asserting strongly enough
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```py
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a = "python"
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@ -2246,7 +2269,12 @@ b = "javascript"
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* For 1, the correct statement for expected behavior is `x, y = (0, 1) if True else (None, None)`.
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* For 2, the correct statement for expected behavior is `t = ('one',)` or `t = 'one',` (missing comma) otherwise the interpreter considers `t` to be a `str` and iterates over it character by character.
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* `()` is a special token and denotes empty `tuple`.
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* For 3, no `AssertionError` was raised because we're asserting entire tuple, instead of asserting the individual expression `a == b`. The following snippet will clear things up,
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* In 3, as you might have already figured out, there's a missing comma after 5th element (`"that"`) in the list. So by implicit string literal concatenation,
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```py
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>>> ten_words_list
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['some', 'very', 'big', 'list', 'thatconsists', 'of', 'exactly', 'ten', 'words']
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```
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* No `AssertionError` was raised in 4th snippet because instead of asserting the individual expression `a == b`, we're asserting entire tuple. The following snippet will clear things up,
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```py
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>>> a = "python"
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>>> b = "javascript"
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@ -2324,7 +2352,62 @@ Same result, that didn't work either.
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["wtf"]
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```
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---
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### ▶ Wild imports
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```py
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# File: module.py
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def some_weird_name_func_():
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print("works!")
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def _another_weird_name_func():
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print("works!")
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```
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**Output**
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```py
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>>> from module import *
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>>> some_weird_name_func_()
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"works!"
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>>> _another_weird_name_func()
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Traceback (most recent call last):
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File "<stdin>", line 1, in <module>
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NameError: name '_another_weird_name_func' is not defined
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```
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#### 💡 Explanation:
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- It if often adivsable to not use wildcard imports. In wildcard imports, the names with leading underscore are be imported. This may lead to errors in runtime.
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- Had we used `from ... import a, b, c` syntax, the above `NameError` won't have occurred.
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```py
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>>> from module import some_weird_name_func_, _another_weird_name_func
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>>> _another_weird_name_func()
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works!
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```
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- If you really want to use wildcard imports, then you'd have to define the list `__all__` in your module that will contain a list of public objects that'll be available when we do wildcard imports.
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```py
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__all__ = ['_another_weird_name_func']
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def some_weird_name_func_():
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print("works!")
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def _another_weird_name_func():
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print("works!")
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```
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**Output**
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```py
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>>> _another_weird_name_func()
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"works!"
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>>> some_weird_name_func_()
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Traceback (most recent call last):
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File "<stdin>", line 1, in <module>
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NameError: name 'some_weird_name_func_' is not defined
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```
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---
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---
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@ -2622,12 +2705,12 @@ The spelling is intended. Please, don't submit a patch for this.
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class Yo(object):
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def __init__(self):
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self.__honey = True
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self.bitch = True
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self.bro = True
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```
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**Output:**
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```py
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>>> Yo().bitch
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>>> Yo().bro
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True
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>>> Yo().__honey
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AttributeError: 'Yo' object has no attribute '__honey'
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@ -2635,7 +2718,7 @@ AttributeError: 'Yo' object has no attribute '__honey'
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True
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```
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Why did `Yo()._Yo__honey` work? Only Indian readers would understand.
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Why did `Yo()._Yo__honey` work?
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#### 💡 Explanation:
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@ -2645,6 +2728,10 @@ Why did `Yo()._Yo__honey` work? Only Indian readers would understand.
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---
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---
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## Section: Miscellaneous
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