The basic syntax only points out the parts that I am not familiar with
input Output
The same print function prints multiple data
print(1,3,4,5)
#
1 3 4 5
Comma separated will be separated by spaces to print
print print multiple lines of data
print("""aaaa
bbbbbb
cccccc
""")
#
aaaa
bbbbbb
cccccc
Will automatically print out a newline
Data types and variables
Basic data types supported by Python
- Integer
- Floating point number. In addition to standard floating-point number writing, there is also scientific notation that can be used, such as 1e10
- String
Note: When escaping a string, only one/is needed to escape/, not\\\, the output result is/
- bool
String (str)
In a computer, the computer memory is encoded in unicode
In Python 3.x, strings are encoded in unicode
ord function
Use the ord function to view the encoding value. Note that it can only be a single character
print(ord("A"))
# 65
print(ord(" "))
# 20013
chr function
Reverse analysis.
print(chr(65))
# A
Bytes
Since the computer memory can only be encoded in unicode, it is necessary to convert the string to bytes as much as possible. The representation of bytes starts with b, which is similar to x = b"ABC". Pay attention to the difference between "ABC" and b"ABC"
encode function
Convert a string to a sequence of bytes
decode function
Convert the bytes sequence into a string. If a small part of the string cannot be decoded, you can use error=ignore to ignore
print(b"\xe4\xb8\xad\xff".decode(encoding="UTF8", errors="ignore"))
Python beginning comment
#!/usr/bin/env python3
# -*- coding: utf-8 -*-
The first line is only applicable to Unix-like systems and tells the location of the Python interpreter.
The second line tells the Python interpreter how to decode.
Character formatting
The first formatting method
Python s character formatting is similar to the C language
print(" %s, %d " % ("lightingsui", 12))
Use% to separate characters and parameters. If there is only one parameter, you can omit the parentheses, that is
print(" %s" % "lightingsui")
Common placeholders
Placeholder | description |
---|---|
%d | Integer |
%f | Floating point |
%s | String |
%x | Hexadecimal integer |
If you don't want to remember these placeholders, you can just remember %s
, it can format everything.
Of course, you can also specify to output 0 in front or display a few digits after the decimal point when outputting
print("%02d------%.2f" % (1, 0.1345))
# 01------0.13
If you want to output% in a string, you can use %% for output
print("%s---%%" % "sdas")
# sdas---%
If there is no placeholder specified in it, it can be output directly without escaping
The second formatting method
Another way to format a string is to use a string format()
method, which replaces the placeholders {0}
, {1}
in the string with the passed parameters in turn , but this method is much more troublesome than %:
>>> 'Hello, {0}, {1:.1f}%'.format(' ', 17.125)
'Hello, , 17.1%'