一、Getting Started

如果使用的是mac或linux系统，需要输入 python3
比如运行 python3 app.py

可以直接在终端的>>>符号后执行python代码

print("*" * 10)

1、实现

在相关终端当运行“python”为CPython，这是python的默认实现
Jython -java
IronPython -C#
PyPy -用python的一部分编写的；Subset of python

二、Primitive Types

python中区分大小写，具有不同含义

布尔值始终以大写开头（FALSE也不可以）

is_published = False

pep8规则

1、Strings

三引号用来格式化长字符串

message = """
Hi John,

This is Mosh

Blah blah blah
"""
print(message)

效果：

Hi John,

This is Mosh

Blah blah blah

变量[头下标:尾下标]（后面那个是开区间）

course = "Python Programming"
print(len(course))
print(course[0])
print(course[-1])
print(course[0:3])
print(course[0:])
print(course[:3])
print(course[:])

效果：

18
P
g
Pyt
Python Programming
Pyt
Python Programming

2、Escape Sequences

course = 'Python "Programming'
print(course)

Python "Programming

course = "Python \"Programming"
print(course)

Python "Programming

\' \" \\ \n

3、Formatted Strings

first = "Mosh"
last = "Hamedani"
# full = first + " " + last
full = f"{first} {len(last)}"
print(full)

Mosh 8

也可以{2 + 2}

4、String Methods

python中所有东西都是对象

upper函数返回一个新的字符串，因此原先的字符串没有被改变

course = "Python Programming"
course_capital = course.upper()
print(course_capital)
print(course)

PYTHON PROGRAMMING
Python Programming

同上，lower()；title()（将所有单词！的第一个字符大写）

course = "python programming"
print(course.title())

Python Programming

strip()将开头和结尾的所有空格去除，因此分别有lstrip()和rstrip()
find("pro")返回pro的下标，注意python大小写敏感。如果找不到返回-1
replace("p", "j")将所有p换成j
print("Pro" in course)返回的是布尔值，“True”；同理还有not in

5、Numbers

python中有三种numbers（第三种是complex number）

x = 1
x = 1.1
x = 1 + 2j # a + bi

print(10 / 3)
print(10 // 3)
print(10 ** 3)

3.3333333333333335
3
100

6、Working with Numbers

import math

print(round(2.9))
print(abs(-2.9))

print(math.ceil(2.2))

7、Type Conversion

用户输入的永远是字符串！

x = input("x: ")
print(type(x))
y = int(x) + 1
print(f"x: {x}, y: {y}")

# int(x)
# float(x)
# bool(x)
# str(x)

x: 2
<class 'str'>
x: 2, y: 3

8、Quiz

fruit = "Apple"
print(fruit[1:-1])

ppl

三、Control Flow

1、Comparison Operators

10 == "10" # False

因为这两个类型不同，而且在计算机内存中存放在不同地方

"bag" > "apple" # True

"bag" == "BAG" # False
ord("b") # 98
ord("B") # 66

2、Conditional Statements

temperature = 35
if temperature > 30:
    print("It's warm")
    print("Drink Water")
elif temperature > 20:
    print("It's nice")
else:
    print("It's cold")
print("Done")

3、Ternary Operator

age = 22
message = "Eligible" if age >= 18 else "Not eligible"

4、Logical Operators

and or not

5、Short-circuit Evaluation

in Python logical operators are short circuit

6、Chaining Comparison Operators

age = 22
if 18 <= age < 65:
    print("Eligible")

7、For Loops

for number in range(3):
    print("Attemp", number)

Attemp 0
Attemp 1
Attemp 2

可以看出print自动换行，range(x)是[0, x - 1]

for number in range(3):
    print("Attemp", number + 1, (number + 1) * ".")

for number in range(1, 4):
    print("Attemp", number, number * ".")

Attemp 1 .
Attemp 2 ..
Attemp 3 ...

for number in range(1, 10, 2):
    print("Attemp", number, number * ".")

Attemp 1 .
Attemp 3 ...
Attemp 5 .....
Attemp 7 .......
Attemp 9 .........

8、For…Else

Note: The else block will NOT be executed if the loop is stopped by a break statement.

successful = False
for number in range(3):
    print("Attemp")
    if successful:
        print("Successful")
        break
else:
    print("Attempted 3 times and failed")

Attemp
Attemp
Attemp
Attempted 3 times and failed

如果将上述的successful值设置为True：

Attemp
Successful

9、Iterables

print(type(5))
print(type(range(5)))

<class 'int'>
<class 'range'>

# Iterable
for x in "Python":
    print(x)

for x in [1, 2, 3, 4]:
    print(x)

10、While Loops

number = 100
while number > 0:
    print(number)
    number //= 2

100
50
25
12
6
3
1

四、Functions

1、Arguments

def greet(first_name, last_name):
    print(f"Hi {first_name} {last_name}")
    print("Welcome aboard")

greet("Mosh", "Hamedani")

2、Types of Functions

def greet(name):
    print(f"Hi {name}")


def get_greeting(name):
    return f"Hi {name}"


message = get_greeting("Mosh")
file = open("content.txt", "w")
file.write(message)

open()返回一个file对象
然后调用file的write方法

3、Default Arguments

def increment(number, by=1):
    return number + by


print(increment(2, 5))

7

4、*args

函数中数量可变的arguments

*产生的是元组

def multiply(*numbers):
    print(numbers)


multiply(2, 3, 4, 5)

(2, 3, 4, 5)

def multiply(*numbers):
    total = 1
    for number in numbers:
        total *= number
    return total


print(multiply(2, 3, 4, 5))

5、**args

**产生的是字典

def save_user(**user):
    print(user)
    print(user["id"])


save_user(id=1, name="John", age=22)

{'id': 1, 'name': 'John', 'age': 22}
1

6、Scope

message = "a"


def greet(name):
    global message
    message = "b"


greet("Mosh")
print(message)

b

it will realize that in this function we want to use the global message variable, so it will not define a local variable in this function

五、Data Structures

0、Python Collections (Arrays)

There are four collection data types in the Python programming language:

• List is a collection which is ordered and changeable. Allows duplicate members.
• Tuple is a collection which is ordered and unchangeable. Allows duplicate members.
• Set is a collection which is unordered, unchangeable*, and unindexed. No duplicate members.
• Dictionary is a collection which is ordered** and changeable. No duplicate members.

1、Lists

Lists are used to store multiple items in a single variable.

Lists are one of 4 built-in data types in Python used to store collections of data, the other 3 are Tuple, Set, and Dictionary, all with different qualities and usage.

Lists are created using square brackets []

List items are ordered, changeable, and allow duplicate(items with the same value) values.

List items are indexed, the first item has index [0], the second item has index [1] etc.

numbers = [1, 2, 3, 4, 5]
numbers[0] # returns the first item
numbers[1] # returns the second item
numbers[-1] # returns the first item from the end
numbers[-2] # returns the second item from the end


print(len(numbers))


numbers.append(6) # adds 6 to the end
numbers.insert(0, 6) # adds 6 at index position of 0
numbers.remove(6) # removes 6
numbers.pop() # removes the last item
numbers.clear() # removes all the items
numbers.index(8) # returns the index of first occurrence of 8
numbers.sort() # sorts the list
numbers.reverse() # reverses the list
numbers.copy() # returns a copy of the list 

List items can be of any data type:
String, int and boolean data types:

list1 = ["apple", "banana", "cherry"]
list2 = [1, 5, 7, 9, 3]
list3 = [True, False, False]

A list can contain different data types:

list1 = ["abc", 34, True, 40, "male"]

mylist = ["apple", "banana", "cherry"]
print(type(mylist)) # <class 'list'>

It is also possible to use the list() constructor when creating a new list.

thislist = list(("apple", "banana", "cherry")) # note the double round-brackets
print(thislist)