python 打印“你好世界”与“你好世界”

Question

>>> print "hello world"
hello world
>>> "hello world"
'hello world'
>>> 

What is the difference?

A complete noob question.

python hello world example mostly uses

print "hello world"

Can I strip that print and just use "Hello world" for giving a python introduction?

Answer 1

The difference is that print calls str whereas the default action of the REPL (read evaluate print loop) is to call repr on the object unless it is None .

Note that if you aren't working in the interactive interpreter (you're not in the REPL), then you won't see any output in the version without print .

Also note that there is a difference between the output. repr adds quotes on strings.

Answer 2

If you substitute the space for a newline, you'll see they don't even really work the same in the REPL.

>>> print "hello\nworld"
hello
world
>>> "hello\nworld"
'hello\nworld'

If you try to use

"hello\nworld"

by itself in a program, you will get no output of course

Answer 3

If you know a bit of Bash scripting, you'll found by echo '$HOME' will print $HOME letter and not the actual value in $HOME, by that I mean /home/user/.

So as Python, however, print function will interpreted as double quotes and single quote as the same thing. I just use "" if there is no quotes or a sentence that don't have to use double quotes. Although, you still can do that with \\".

Example -

print 'hello\nworld' -> hello
                        world

print "hello\nworld" -> hello
                        world

and

'hello\nworld' -> hello\nworld

If sometimes, I need raw output, I will not use print or try other workarounds.

Also, if I have to use print function to output raw strings. I just use this -

print repr("hello\n\tworld\\") -> 'hello\n\tworld\\'

It depends on your condition, though.

Feel free to edit/suggest for better improvements of this reply. I may do a lot of mistakes and misinformations in this answer.

Answer 4

This is a very good question, in fact, the same doubt I had while I started to learn Python. First, we'll observe the different outputs of these two different programs.

Program type 1

>>> print "hello world"
hello world

The programs using print function, as we know is used to print the given string or numeric data.

Program type 2

>>> "hello world"
'hello world'
>>> 'hello world'
'hello world'

When the print function is not used, and the string is directly told to be printed by giving it within single/double quotes, the answer also gets printed within quotes. We don't need this type of outputs for our programs, even though it might be easy to not use the print command.

This is possible only in Python Command Line. It is not possible if the program is saved in a separate file and will be executed totally.

Answer 5

You are running on python interactive shell.

print "hello world" You have executed a function call that print function executed and output the string you given to the stream file which default is stdout https://docs.python.org/3/library/functions.html#print

>>> "hello world" Is just let python interpreter excute a line of code which is only a string. Since you are running on python interactive shell. The shell will display the string "hello world" to the screen.

Answer 6

It is the fact that you are using python shell that it does anything at all. to prove it, if you actually use a python file, it does nothing at all

 Python 3.7.7 (tags/v3.7.7:d7c567b08f, Mar 10 2020, 10:41:24) [MSC v.1900 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license()" for more information.
>>> 
==== RESTART: C:/Users/s-wan/AppData/Local/Programs/Python/Python37/testhelloworld.py ===
>>> 

but if you actually use it in shell, then it prints the thing out with single quotes:

>>> "Hello World"
'Hello World'

using

print('hello world')

will print 'hello world' without quotes. the shell and the actual file can produce different results.

Answer 7

wow...

>>> print("hello\nworld")

hello world

"hello\\nworld" 'hello\\nworld' 'hello\\nworld' 'hello\\nworld'

Answer 8

只有在命令行中才能避免使用打印功能，否则必须使用打印功能