"if statement" in python

I have the code below (attach). What I want to do is to prompt a user to enter a ticker from Quandl website (financial/economic data) so that the dataset is retrieved. One condition, the data should be of 1-month length starting from the time when a user enters ticker.Let'say if the program is run on 22/01/2018 so the data should be from 22/12/2017 till 22/01/2018 (That is the first thing I am struggling with). Second, I want to make sure that the ticker is entered correctly, so I want to make a condition such that "if the command "quandl.get("ticker", start_date=trim_start, end_date=trim_end)" does not retrieve the data- re-enter the ticker" Please, advise me this issue.

'''Installation steps - go to "Command line" and pass "pip install quandl"'''
 import quandl                        #To extract the data from Quandl 
 website
 import matplotlib.pyplot as plt      #Plotting library
 import datetime
def MainFormula():
ticker = None 
while ticker is None:
    ticker = input("Please, enter stock ticker (should be available in Quandl Website): ")
    try:
        trim_end=datetime.datetime.now()
        trim_start= trim_end - 30
        if quandl.get("ticker", start_date=trim_start, end_date=trim_end) == True:
            print("Here are the results: ")             
        else:            
            print("Please, enter correct stock ticker (check Quandl website)! ")
    except ValueError as e1:
        print("Please, enter correct alpha (should be float - example: 0.2) ")                 

 program = MainFormula()               
 print(program)