Python notes-1 syntax analysis

I haven't written an article for a long time. I recently prepared a Python website and reviewed it. Since I wrote an article, I wrote it according to the specifications on the official website.

You are welcome to point out something wrong.

I. logical and physical rows

A Python program analyzes a symbolic (TAG) stream through a syntax analyzer. It is composed of a series of logical rows, which are composed of one or more physical rows.

What is logic? A logical line is a statement that implements a function.

a = 1print(3)

The above example explains: Here a = 1, assigning a value to a is a logical line; printing a number 3 on the screen is also a logical line.

A physical row is an integral part of a logical row, because a logical row may consist of several physical rows.

print3

In the preceding example, print is a physical row, and 3 is a physical row, which forms a logical row.

However, in the if Condition Statement, assume that there are two conditions: 1> 0 and 2> 0. if yes, output 3. Therefore, the two conditions cannot be directly separated.

You can write it as follows:

If 1> 0 \ # Or if 1> 0 and \ and 2> 0: #2> 0: print (3) # print (3)

In the preceding example, an explicit row connection ("\") is added after and, which helps two physical rows join together to form a logical row.

In addition, # is used in python to annotate the code.

Ii. indentation

In Python, there are two kinds of indentation: one is to press a space, and the other is to press the tab key.

The Python syntax stipulates that the first line of a program cannot contain spaces.

The tab key contains eight spaces (this is the same in UNIX as it was found when I was bored. You can count it if you don't believe it ~ _~).

Iii. Literal

Here we will give a general explanation of the expressions of numbers, texts, symbols, and other texts.

1. escape characters:

The escape characters inherit the C style in python. The common \ n, \ B, \ t are used in the same way as C.

2. Integer:

Decimal: "1"... "9"... "0"

Octal: "0" ("o" | "O") "1"... "9" "0"

Binary: "0" ("B" | "B") "1"... "9" "0"

Hexadecimal: "0" ("x" | "X") "1"... "9" "0"

3. floating point float:

There are several forms, 3.14 10 .. 001 1e100 3.14e-10 0e0

4. Plural:

In python, there are also such types as: 3.14j, 10.j, 10j,. 001j, 1e100j, 3.14e-10j

5. operators:

+       -       *       **      /       //      %<<      >>      &       |       ^       ~<       >       <=      >=      ==      !=

Iv. Summary

Let's talk about the python syntax first. In the next article, I will describe details about the python data type.