Unable to pass text to an HTML5 dialog box via Appium sendKeys() command

I am using Python in conjunction with Appium to automate testing on an Android mobile device. I am using the Appium/Selenium webdriver and launching Chrome on the device. There is a dialog that I am targeting with a username field and I am able to find the Username textbox via XPath and even click into it to start typing. However when I use the sendKeys() command to enter text into into, it does nothing. Any help will be much appreciated.

Code (Python):

    try:
        self.prac_btn = self.get_ele('xpath', '//*[@id="dialogMessage"]/fieldset/input[1]')
        print "Found username"
    except:
        print "Cannot find username"

    try:
        time.sleep(5)
        self.click_ele(self.prac_btn)
    except:
        print "Cannot click on username"

    try:
        time.sleep(5)
        self.prac_btn.send_keys(self, "Username")
    except:
        print "Cannot type text"

Solution

The error is caused by passing two arguments to send_keys(), which only accepts one argument. self is not needed as an argument because send_keys() is a class instance function. self is passed implicitly.

This is also a good example of why a bare except is dangerous. If you had caught the exception and printed it, you would have seen something like this:

TypeError: send_keys() takes exactly 1 argument (2 given)

Which would have been a strong clue as to what went wrong.