The first day of formal learning python

• pycharm install and simple to use
  • Supporting the development of software, code line by line debugging, high-end design
• Compiled: disposable compiled into binary, and then executed.

Advantages: high efficiency.

Disadvantages: can not cross-platform.

Representatives language: c

• Interpreted: Progressive interpreted as a binary, and then executed.

Advantages: cross-platform, high development efficiency.

Disadvantages: low efficiency.

Representatives Language: python

• Coding acquaintance

  Computer storage file, storing data, and sent across the network, the underlying transmission data are stored 01010101.

  First edition: No Dan;

  110 I

  111 and

  101 you

  second edition:

  0000110 I

  0000111 and

  0000101 You

  Codebook: The relationship between binary and text 0101011001

  The earliest this password:

  1.ASCII code: only contain letters, numbers, special characters (8).

  Seven segment can represent 128 different characters, 7 2 **

  0 000 000: a

  0 000 000: b

  ASCII code set aside a total of eight, 8 bit is 0;

  I.e., one byte 0000 0001 is called: 8bit = 1byte (bytes)

  1. China: gbk (can represent up to 2 ** 16 Chinese, namely 65535): contains only letters, numbers, special characters (ASCII) and Chinese, also known as GB (national standards); a letter with a byte , a Chinese two bytes.

  3.Unicode: Unicode: all the text on the world record this password to this.

  Initially, a character represented by 2 bytes:

  0000 0001 0000 0011 : a

  Later, to cover all, with 4 bytes, it can represent 2 ** 32 = 4,294,967,296 characters.

  But the world's full text of no more than 2 ** 21 characters

  utf-8: Minimum represented by one byte characters (English), European by 2 bytes, three bytes Chinese

  'We 12ax': GBK: 8 bytes

  'We 12ax': UTF-8: 10 bytes

  Unit conversion:

  8bit = 1byte

  1024byte = 1kb

  1024kb = 1MB

  1024MB = 1GB

  1024GB = 1TB

  1024TB = 1PB There EB ZB YB NB common enough to TB

1. variable:

   • Numbers, letters, underscores in any combination.
   • You can not begin with a number
   • You can not use python Keywords: print, if ......
   • You can not use Chinese
   • Descriptive

2. Variables and data types of differences:

   •  name = 'a'
      name = 'b'
      print(name)
      name = 'c'
      print(name)

   • Steady

     • It has been the same amount, with almost the same variable.

       python using all uppercase letters, said:

       NAME='a'#放在代码最前方，提示人此变量不可更改（实际上可以更改）

3. Basic data types:

   • 1,2,3,3002, int digits, + -? % ** ......
   • 'Fasz be 2' str string + * int
   • True False boll Boolean value

4. A user input input ()

5. if (top to bottom are performed to meet the conditions of one code block, wherein if the flow exit)

   • if conditions:
   • if else：
   • if elif elif ....
   • if nested

6. while loop

   • why：

   • how：

     The basic structure:

     while 循环条件:
         循环体

     • First determine whether the conditions True

     • If it is True, then enter the body of the loop

     • Cycle and then determine the conditions, if it is True, then re-enter the cycle, if it is False then exit the loop.

   • Terminator Cycle:

     • Changing conditions
     • break: exit the loop
     • continue: terminate this cycle into the next cycle.

   • while else: if not terminated break while the else statement will be executed, while if the break is terminated, break statements are executed.

     count=1
     while count<=3:
         print(count)
         count+=1
     else:
         print('我被执行了')
     

     count=1
     while count<=3:
         print(count)
         break
     else:
         print('我被执行了')#此句未被执行

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