Summary of generator and file system knowledge of Python basic learning

Time:2022-1-8

1、 Generator

First, explain the iterator.

The ability to iterate over sequences in a consistent way (such as objects in a list or lines in a file) is an important feature of Python. This is achieved through a method called iterator protocol, which is a general way to make objects iteratable

Now, a native method of making objects iteratable.

some_ dict = {"a": 1, "b": 2, "c": 3}  

An iterator is a special object that can be passed to a Python interpreter in a context such as a for loop. Most methods that accept objects such as lists can also accept any iteratable object. For example, built-in methods such as min, Max, sum, and type constructors such as list and tuple.

dict_ iterator=iter(some_dict)

A generator is a simple way to construct new iteratable objects。 General functions only return a single value after execution, while the generator returns a value sequence in a delayed manner, that is, it pauses after each value is returned until the next value is requested. To create a generator, simply replace return in the function with yeild.

def squares(n=10):

Output:

<generator object squares at 0x7f3a75af4a00>
Generating squares from 1 to 100
(1,)
(4,)
(9,)
(16,)
(25,)
(36,)
(49,)
(64,)
(81,)
(100,)

Another more concise way to construct a generator is to use generator expression. This is a generator similar to list, dictionary, set derivation. AttentionThe creation method is to change the square brackets at both ends of the list derivation formula into parentheses:

gen=(x**2 for x in range(5))

2、 File system

The built-in open function parameters are as follows:

Summary of generator and file system knowledge of Python basic learning

Common file methods

Summary of generator and file system knowledge of Python basic learning

#With the statement, you can easily clean up the open file and automatically close the file stream when the run is almost finished

with open(path) as f: 
    lines=[x.strip() for x in f]

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