笨方法学python3

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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)

  

  

 

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