笨方法学python3

阅读《笨方法学python3》，归纳的知识点

相关代码详见github地址：https://github.com/BMDACMER/Learn-Python

习题1：安装环境+练习  print函数使用  主要区别双引号和单引号的区别

习题2：注释符号#

习题3：运算符优先级，跟C/C++， Java类似

以下运算符优先级：从下往下以此递增，同行为相同优先级

Lambda  #运算优先级最低
逻辑运算符: or
逻辑运算符: and
逻辑运算符:not
成员测试: in, not in
同一性测试: is, is not
比较: <,<=,>,>=,!=,==
按位或: |
按位异或: ^
按位与: &
移位: << ,>>
加法与减法: + ,-
乘法、除法与取余: *, / ,%
正负号: +x,-x

习题4：变量名+打印 介绍了以下这种形式的打印

print("There are", cars, "cars available.")　　

习题5：更多打印方式    比如 f"XXX"

my_name = 'Zed A. Shaw'

print(f"Let's talk about {my_name}")

习题6：继续使用f"XX"打印

习题7：format打印方式，可采用end=‘ ’代替换行

print("Its fleece was white as {}.".format('show'))
print(end1 + end2 + end3 + end4 + end5 + end6, end=' ')
print(end7 + end8 +end9 + end10 +end11 + end12)

显示如下：
Its fleece was white as show.
Cheese Burger

习题8：更多打印方式（这种打印方式见的较少）

formatter = '{} {} {} {}'

print(formatter.format(1, 2, 3, 4))
print(formatter.format("one", "two", "three", "four"))
print(formatter.format(True, False, False, True))
print(formatter.format(formatter, formatter, formatter, formatter))
# print("\n")
print(formatter.format(
    "Try your",
    "Own text here",
    "Maybe a poem",
    "Or a song about fear"
))

显示如下：
1 2 3 4
one two three four
True False False True
{} {} {} {} {} {} {} {} {} {} {} {} {} {} {} {}
Try your Own text here Maybe a poem Or a song about fear　　

　　

习题9：多行打印，换行打印

小结：打印方式

1）print("There are", cars, "cars available.")  # 变量名直接打印
2）print(f"Let's talk about {my_name}") # 带有f"{}"的打印方式
3） 变量名+format()

hilarious = False
joke_evaluation = "Isn't that joke so funny?! {}"

print(joke_evaluation.format(hilarious))

4）print("Its fleece was white as {}.".format('show'))  #
5）formatter = '{} {} {} {}'
    print(formatter.format(1, 2, 3, 4))
    print(formatter.format("one", "two", "three", "four"))
6）print('''
There's something going on here.
With the three double-quotes.
We'll be able to type as much as we like.
Even 4 lines if we want,or 5,or 6
'''）                                                  # 多行打印     

　　

习题10：转义字符

习题11：介绍 input()函数，并使用到习题5介绍的打印方式

print("How old are you?", end=' ')
age = input()
print("How tall are you?", end=' ')
height = input()
print("How much do you weight?", end=' ')
weight = input()

print(f"So,you're {age} old,{height} tall and {weight} heavy.")　　

习题12：介绍input()函数   加提示符

age = input("How old are you?")

print("How old are you? {}".format(input()))   # 先运行后面的在运行前面的提示

习题13： 参数、解包和变量

from sys import argv
# read the WYSS section for how to run this
script, first, second, third = argv

print("The script is called:", script)
print("Your first variable is:", first)
print("Your second variable is:", second)
print("Your third variable is:", third)

# 注： 把argv中的东西取出，解包，将所有的参数依次复制给左边的这些变量
>>python ex13.py first second third

　　

练习14：提示与传递   主要讲解 input()函数 配合输入格式

from sys import argv
'''
PS E:\dev\code\笨方法学python3> python ex14.py Zed
Hi Zed,I'm the ex14.py script.'
I'd like to ask ypu a few questions.
Do ypu like me Zed?
>yes
Where do ypu live Zed?
>yicheng
What kind of computer do you have?
>Dell
'''
script , user_name = argv
prompt = '>'

print(f"Hi {user_name},I'm the {script} script.'")
print("I'd like to ask you a few questions.")
print(f"Do ypu like me {user_name}?")
likes = input(prompt)

print(f"Where do you live {user_name}?")
lives = input(prompt)

print("What kind of computer do you have?")
computer = input(prompt)

print(f'''
Alright, so you said {likes} about liking me.
You live in {lives}. Not sure where that is.
And you have a {computer} computer. Nice.
''')

　　

练习15：读取文件

txt = open(filename)
print(f"Here's your file {filename}:")
print(txt.read())
txt.close()

练习16：读写文件

close:关闭文件。跟你的编辑器中的“文件”->“保存”是一个意思
read：读取文件的内容
readline：只读取文本文件中的一行
truncate：清空文件，请小心使用该命令
write('stuff')：将“stuff”写入文件
seek（0）： 将读写位置移动到文件开头　　

练习17：继续读写文件

in_file = open(from_file)
indata = in_file.read()

out_file = open(to_file,'w')
out_file.write(indata)

　　

练习18：函数

练习19：函数与变量

pytyon在定义函数的时候跟C/C++区别蛮大，python不需要定义参数类型，定义某一函数时 可参考如下：

def function(vailable1, vailable2,*):

练习20： 函数和文件

from sys import argv

script, input_file = argv

def print_all(f):
    print(f.read())

def rewind(f):
    f.seek(0)

# 带有行号的打印内容
def print_a_line(line_count,f):
    print(line_count, f.readline())

current_file = open(input_file)     # 接受的参数，打开文件

print("First let's print the whole file:\n")

print_all(current_file)          # 打印该文件

print("Now let's rewind, kind of like a tape.")

rewind(current_file)     # 将读写位置移动到文件开头（第一个字符的前面一个位置） 方便后续读取   如不执行该操作，后续打印为空

print("Let's print three lines:")

current_line = 1
print_a_line(current_line,current_file)

current_line = current_line + 1
print_a_line(current_line,current_file)

current_line = current_line + 1
print_a_line(current_line, current_file)