Create unit3_ex3.4.2.py

unit3_ex3.4.2.py

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+# exercise 3.4.2 from unit main
+'''
+Write a program that accepts a string of his choice from the user.
+The program will print to the screen a string in which all occurrences
+of the first character have been replaced by the character 'e', except for the first
+character itself.
+
+example: 
+Please enter a string: ddar astronaut. pldase, stop drasing md!
+dear astronaut. please, stop erasing me!
+
+'''
+
+str = input("Enter a string: ")
+char_to_replace = str[0]
+if(len(str) > 1):
+  output = str[0] + str[1:].replace(char_to_replace, 'e')
+else:
+  output = str[0]
+
+print(output)
+