title: Python If & Dictionary Usage in Address book program
body: <p>I am making a small address book program as practice, do you know what's wrong with my code when I tried to add new entry?</p>
  
  <p>Also, how can I make it go back to choose 1-4 instead of keep in the same sub condition like error 2?</p>
  
  <p>Thanks so much!</p>
  
  <pre><code>print('|-----Welcome to Q\'s Addrss Book-------|')
  print('|--------------------------------------|')
  print('|Please choice from the following:-----|')
  print('|----------1: Find   Contacts----------|')
  print('|----------2: Add    Contacts----------|')
  print('|----------3: Delete Contacts----------|')
  print('|----------4: Quit Address Book--------|')
  
  i = int(input('Can I help you? :'))
  address = {'ray':1234,'simon':2345,'alen':8888}
  while 1:
      if i == 1:
          x=input('What\'s his/her name?')
          print(address[x])
  
      if i == 2:
          x = (input('New Contact name?'))
          if address[x] is not None:
              z = str(input('Contact'+x+' with phone number: '+str(address[x])+ ' address already existed, do you want to override?(Yes/No)'))
              if z == 'yes':
                  address[x] = input('New number?')
              elif z == 'no':
                  break
              else:
                  print('Please choose yes or no')
          else:
              address[x] = input('New number?')
  
      if i == 3:
          z = input('Who you want to delete:')
          if address[z] is not None:
              del address[z]
          else:
              print('Contact not existed!')
  
      if i == 4:
          break
  </code></pre>
  
  <p>Error1:</p>
  
  <pre><code>&gt;&gt;&gt; 
  |-----Welcome to Q's Addrss Book-------|
  |--------------------------------------|
  |Please choice from the following:-----|
  |----------1: Find   Contacts----------|
  |----------2: Add    Contacts----------|
  |----------3: Delete Contacts----------|
  |----------4: Quit Address Book--------|
  Can I help you?:2
  New Contact name?q
  Traceback (most recent call last):
    File "/Users/xxx/Documents/1.py", line 18, in &lt;module&gt;
      if address[x] is not None:
  KeyError: 'q'
  &gt;&gt;&gt; 
  </code></pre>
  
  <p>Error 2: keep looping in a sub if condition:</p>
  
  <pre><code>&gt;&gt;&gt; 
  |-----Welcome to Q's Addrss Book-------|
  |--------------------------------------|
  |Please choice from the following:-----|
  |----------1: Find   Contacts----------|
  |----------2: Add    Contacts----------|
  |----------3: Delete Contacts----------|
  |----------4: Quit Address Book--------|
  Can I help you?:1
  What's his/her name?ray
  1234
  What's his/her name?
  &gt;&gt;&gt;
  </code></pre>
  
  <p>Ok, thanks for all your guys, I have made it work, here is the correct code:</p>
  
  <pre><code>print('|-----Welcome to Q\'s Addrss Book-------|')
  print('|--------------------------------------|')
  print('|Please choice from the following:-----|')
  print('|----------1: Find   Contacts----------|')
  print('|----------2: Add    Contacts----------|')
  print('|----------3: Delete Contacts----------|')
  print('|----------4: Quit Address Book--------|')
  
  
  address = {'ray':123456789,'simon':222222222,'alen':88888888}
  while 1:
      i = int(input('Can I help you?'))
      if i == 1:
          x=input('What\'s his/her name?')
          if x in address:
              print(address[x])
          else:
              print('Contact does not exist!')
  
      if i == 2:
          x = (input('New Contact name?'))
          if x in address:
              z = str(input('Contact'+x+' with phone number: '+str(address[x])+ ' address already existed, do you want to override?(Yes/No)'))
              if z == 'yes':
                  address[x] = input('New number?')
              elif z == 'no':
                  continue
              else:
                  print('Please choose yes or no')
          else:
              address[x] = input('New number?')
  
      if i == 3:
          z = input('Who you want to delete:')
          if z  in address:
              del address[z]
          else:
              print('Contact does not exist!')
  
      if i == 4:
          break
  </code></pre>