In python3 print('\n') will generate an extra blank line. Could someone make a brief explanation about this?
Thanks in advance.
In the documentation for print it is stated that:
All non-keyword arguments are converted to strings like str() does and written to the stream, separated by sep and followed by end.
The default value for end is '\n', so Python first prints the supplied '\n' and then end which equals '\n' too; that's why you see two blank lines.
Change the default value if you don't want that:
print('\n', end='')
Note that this also applies to Python 2.x's print statement, it also writes '\n' at the end. You can change the behavior there by appending a comma character.
Related
I am writing a program in Python and want to replace the last character printed in the terminal with another character.
Pseudo code is:
print "Ofen",
print "\b", # NOT NECCESARILY \b, BUT the wanted print statement that will erase the last character printed
print "r"
I'm using Windows8 OS, Python 2.7, and the regular interpreter.
All of the options I saw so far didn't work for me. (such as: \010, '\033[#D' (# is 1), '\r').
These options were suggested in other Stack Overflow questions or other resources and don't seem to work for me.
EDIT: also using sys.stdout.write doesn't change the affect. It just doesn't erase the last printed character. Instead, when using sys.stdout.write, my output is:
Ofenr # with a square before 'r'
My questions:
Why don't these options work?
How do I achieve the desired output?
Is this related to Windows OS or Python 2.7?
When I find how to do it, is it possible to erase manually (using the wanted eraser), delete the '\n' that is printed in python's print statement?
When using print in python a line feed (aka '\n') is added. You should use sys.stdout.write() instead.
import sys
sys.stdout.write("Ofen")
sys.stdout.write("\b")
sys.stdout.write("r")
sys.stdout.flush()
Output: Ofer
You can also import the print function from Python 3. The optional end argument can be any string that will be added. In your case it is just an empty string.
from __future__ import print_function # Only needed in Python 2.X
print("Ofen",end="")
print("\b",end="") # NOT NECCESARILY \b, BUT the wanted print statement that will erase the last character printed
print("r")
Output
Ofer
I think string stripping would help you. Save the input and just print the string upto the length of string -1 .
Instance
x = "Ofen"
print (x[:-1] + "r")
would give you the result
Ofer
Hope this helps. :)
I was wondering what the comma in the middle of print is used for?
This code:
print('No. of lower case letters : ', d['lower'])
A bit of history
Since Python 3, there is actually no print statement. Print is a function just like any other (In the now obsolete Python 2, print was indeed actually a statement).
A special case in Python 2 is that you could indeed have a comma at the end, such like
print "my string",
This would print the string with a space rather than a line feed as the terminator, allowing multiple print statements to contribute to one line. But forget about all this now, Python 2 is long gone (well, since January 2020).
Now to your question.
All functions in Python accept a number of arguments separated by a comma. The print function is no different. The print function takes any number of positional arguments, as well as a number of well-known named arguments, e.g.
print(a,b,c, file=f)
will send the positional arguments a, b and c and the keyword argument file. The print function will concatenate all positional arguments (separated by space) when printing them (optionally to the file specified by the file argument, otherwise to standard output).
The comma let's you add multiple arguments to the print statement. It basically lets you print them in succession, separated by a space.
Example:
print('hi', 'hello', 'greetings')
#hi hello greetings
The comma will let you print multiple strings in one calling of the print function. By default, each string will be separated by a space.
These are the arguments for the print function:
print(*objects, sep=' ', end='\n', file=sys.stdout)
You can change the sep argument to something else.
I have the following code when writing to a text file:
def writequiz(quizname,grade,perscore,score,username):
details=[quizname,username,grade,perscore,score]
with open('quizdb','a') as userquiz:
print(details,file=userquiz)
Now the code is doing what I want it to (writing to a new line every time), however if I wanted to write every list to the same line in the text file how would I do this using the print method as used above? I know I could use file.write, but how do I remove the newline character in the print statement? Slightly hypothetical but it was bugging me.
If you are using python 2.x, you can do the following:
print >> userquiz, details, # <- notice the comma at the end
If using pytnon 3.x, you can do this:
print(details,file=userquiz, end = " ")
Check print documentation.
You can set the end parameter of print to be an empty string (or some other character):
print(details, file=userquiz, end='')
From the docs, you can see that it defaults to a newline:
print(*objects, sep=' ', end='\n', file=sys.stdout, flush=False)
Print objects to the text stream file, separated by sep and followed by end. sep, end, file and flush, if present, must be given
as keyword arguments.
This is what is being printed to the file currently.
Hello I am currently working on something and I am trying to print output as such in python
hello=10
but my code below is printing it as such
hello= 10
10 is an int i have tried these codes but none work
print "hello=",10
print "hello=",str(10)
print "hello=",str(10).strip()
i would appreciate the help thank you
Simply concatenate the strings:
print "hello="+str(10)
Use str.format,
print("hello={}".format(10))
PS: The print statement has been replaced with a print() function since Python 3.0.
Old: print x, # Trailing comma suppresses newline
New: print(x, end=" ") # Appends a space instead of a newline
Refer to Print Is A Function for the detailed descriptions.
If you use print with multiple arguments, separated by ,, a single space ' ' is inserted as a separator in between each of those.
When using Python 3's print function, you can specify the sep parameter; default is ' '.
>>> from __future__ import print_function # when in Python 2
>>> print("hello=", 10)
hello= 10
>>> print("hello=", 10, sep="")
hello=10
>>> print("hello=", 10, sep="###")
hello=###10
For Python 2's print statement, there is to the best of my knowledge no such option.
You may also consider using the Python 3 compatible print() function:
This function can be used after a __future__ directive:
from __future__ import print_function
print("hello=", 10, sep='')
Output:
hello=10
The print() function as a sep keyword argument which allows you to replace the space separator by an empty string.
Here is the online help:
Help on built-in function print in module builtins:
print(...)
print(value, ..., sep=' ', end='\n', file=sys.stdout, flush=False)
Prints the values to a stream, or to sys.stdout by default.
Optional keyword arguments:
file: a file-like object (stream); defaults to the current sys.stdout.
sep: string inserted between values, default a space.
end: string appended after the last value, default a newline.
flush: whether to forcibly flush the stream.
The call "print" will place a space for a comma.
Yes, Python provides many ways to print the strings as above mentioned, I still would like to construct the output with C or Java style format:
print "hello=%d" % 10
Just typing print only gives newline in python. Typing print without the brackets in 3.x will also gives a newline. Why?
Because the documentation says so
print(*objects, sep=' ', end='\n', file=sys.stdout, flush=False)
Print objects to the text stream file, separated by sep and followed by end. sep, end and file, if present, must be given as keyword arguments.
All non-keyword arguments are converted to strings like str() does and written to the stream, separated by sep and followed by end. Both sep and end must be strings; they can also be None, which means to use the default values. If no objects are given, print() will just write end.
The file argument must be an object with a write(string) method; if it is not present or None, sys.stdout will be used. Since printed arguments are converted to text strings, print() cannot be used with binary mode file objects. For these, use file.write(...) instead.
Whether output is buffered is usually determined by file, but if the flush keyword argument is true, the stream is forcibly flushed.
Changed in version 3.3: Added the flush keyword argument.
Note that end is defaulted to '\n' which is a new line.
In Python 3, print is now a function. It will print a new line character at the end of your statement.
If you don't specify an "end" it will by default use a new line character.
You can prevent this by doing something such as:
print("hello world", end="")
Because the default parameter in print is \n for the end,
though if you pass parameter for print end variable as \t or space , then you can see the same !
But it works 2.7 and above!
It is interesting how languages differ in this.
print in the Korn shell (ksh) has the same behaviour as python, i.e. it adds a newline. Bash does not have a print, relying on echo instead, which also adds a newline (which, like python, can be suppressed).
print in Perl does not, and caused so much inconvenience that another version, called say, was added which does add a newline.
Ruby and PHP are like Perl in that print also does not add a newline. This of course is less of an issue when embedded in HTML.
If you look at other languages, for example here you will find opinion divided as to whether a newline should be added or not. The removal of the newline in Python is discussed in PEP259.