Python 3.2 - Concatenate and string formatting behavior not behaving as expected

Question

I want to create a "full file name" variable from several other variables, but the string concatenation and string format operations aren't behaving the way I expect.

My code is below:

file_date = str(input("Enter file date: "))

root_folder = "\\\\SERVER\\FOLDER\\"
file_prefix = "sample_file_"
file_extension = ".txt"

print("")
print("Full file name with concatenation: ")
print(root_folder + file_prefix + file_date + file_extension)
print("Full file name with concatenation, without file_extension: ")
print(root_folder + file_prefix + file_date)
print("")

print("")
print("Full file name with string formatting: ")
print("%s%s%s%s" % (root_folder, file_prefix, file_date, file_extension))
print("Full file name with string formatting, without file_extension: ")
print("%s%s%s" % (root_folder, file_prefix, file_date))
print("")

The output when I run the script is:

C:\Temp>python test.py
Enter file date: QT1

Full file name with concatenation:
.txtRVER\FOLDER\sample_file_QT1
Full file name with concatenation, without file_extension:
\\SERVER\FOLDER\sample_file_QT1


Full file name with string formatting:
.txtRVER\FOLDER\sample_file_QT1
Full file name with string formatting, without file_extension:
\\SERVER\FOLDER\sample_file_QT1

I was expecting it to concatenate the ".txt" at the very end, except it's replacing the first four characters of the string with it instead.

How do I concatenate the extension variable to the end of the string instead of having it replace the first n characters of the string?

In addition to how to solve this particular problem, I'd like to know why I ran into it in the first place. What did I do wrong/what Python 3.2 behavior am I not aware of?

bstpierre · Accepted Answer · 2011-06-21 19:40:41Z

8

I think the method input used in your example, like so:

file_date = str(input("Enter file date: "))

may be returning a carriage return character at the end.
This causes the cursor to go back to the start of the line when you try to print it out. You may want to trim the return value of input().

edited Jun 21, 2011 at 19:40

bstpierre

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answered Jun 6, 2011 at 18:32

hopia

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5 Comments

Greg Haskins Over a year ago

Confirmed. After running the OP's code, repr(file_date) is 'QT1\r'

tgxiii Over a year ago

I had a feeling it was something this simple. It was adding a carriage return "\r" instead of line feed, but you helped steer me in the right direction. Thanks!

MRAB Over a year ago

In Python 3, input returns a string, so there's no need to use str.

John Machin Over a year ago

@MRAB: This behaviour appears to be a BUG in Windows Python 3.x; 2.7 raw_input() doesn't leave an unwanted unexpected \r behind. Did you report it?

MRAB Over a year ago

@John: No, it has already been reported (issue #11272). Anyway, I wasn't commenting on the bug, but on the 'str' which isn't necessary because in Python 3 'input' returns a string.

Tim Pietzcker · Accepted Answer · 2011-06-06 18:43:10Z

3

Use this line instead to get rid of the line feed:

file_date = str(input("Enter file date: ")).rstrip()

edited Jun 6, 2011 at 18:43

Tim Pietzcker

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answered Jun 6, 2011 at 18:39

CalMlynarczyk

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