Day 6

Author: codingforentrepreneurs

tutorial-reference/Day 6/Day 6 - String Formatting & Substitutions.md

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+# Day 6 - String Formatting & F-Strings
+Python has ways to make writing text a bit more programmic and helps systematically remove repeating youself.
+
+Also, check out:
+- [pyformat](https://pyformat.info/)
+- [strftime.org](https://strftime.org/)
+
+### String Formatting
+
+Basic formatting:
+
+`#`: Write a comment `# this is a comment`
+
+`\n`: New Line
+
+`\t`: Tab
+
+`\\` or `//`: Allowed Slash
+
+`\'`: Allowed Single Quote
+
+`\"`: Allowed Double quote
+
+`{{` or `}}`: Allowed signle curly bracket in formatted strings
+
+`"your single-line text"`: Wrap a single quote (`'`) or double quote (`"`) around text / numbers to make it a string.
+
+`\`: A `slash` in front of a `return`/`enter` will escape that. Allowing for multi-line strings without the triple quotes. Such as:
+```python
+"this is my string example\
+when I close it here"
+```
+
+
+`""" your multi-line text"""`: Wrap 3x single quotes (```) or 3x double quotes (`"`) around a lot of text to allow for multi-line strings. Such as:
+```python
+"""this is my string example
+when I close it here"""
+```
+
+
+
+#### The `.format()` method
+
+_Empty_
+```python
+"{} {}".format("Hello", "World")
+```
+
+_Positional_
+```python
+"{0} {1} {0}".format("Hello", "World")
+```
+
+_Keyword_
+```python
+"{first} {second} {first}".format(first="Hello", second="World")
+```
+
+_Positional & Keyword_
+```python
+"{0} {second} {0}".format("Hello", second="World")
+
+"{0} {1} {2['hello']}".format("Hello", "World", {'hello': 'sup'})
+```
+
+_Unpacking a Dictionary_
+```python
+data = {'name': 'Hodor', 'email': 'holdthe@door.com'}
+txt = 'Name: {name}\nEmail: {email}'.format(**data)
+print(txt)
+```
+
+_Numbers, Floats & Decimals_
+
+Number / Integer
+```python
+"{:d}".format(32)
+```
+or
+```python
+"{}".format(32)
+```
+
+Float / Decimal
+```python
+"{:f}".format(32)
+```
+
+```python
+pi = 3.14159265359
+"{:f}".format(pi)
+```
+
+Limit to `n` decimal places. Replace `4` below with the number of decimal places to round to.
+```python
+pi = 3.14159265359
+"{:.4f}".format(pi)
+```
+
+
+
+#### The `%` method
+
+_Positional - Strings or Numbers_
+```python
+"%s %s %s %s" % ("Hello", 12, 131.312, {'hello': 'sup'})
+```
+
+_Keyword / Dictionary_
+```python
+"%(first)s %(second)s" % {"first":"Hello", "second":"World"}
+```
+
+_Keywords_ (Also known as named placeholders)
+```python
+data = {'name': 'Hodor', 'email': 'holdthe@door.com'}
+txt = 'Name: %(name)s\nEmail: %(email)s' % data
+print(txt)
+```
+
+_Numbers, Floats & Decimals_
+
+Number
+```python
+"%d" % (32)
+```
+or
+```python
+"%s" % (32)
+```
+
+Float
+```python
+"%f" % (32)
+```
+
+```python
+pi = 3.14159265359
+"%f" % (pi)
+```
+
+Limit to `n` decimal places. Replace `2` below with the number of decimal places to round to.
+```python
+pi = 3.14159265359
+"%.2f" % (pi)
+```
+
+#### `f` Strings (aka `f-string`)
+
+_Strings or Number variables_
+```python
+first = "Hello"
+second = "World"
+third = 32.3122
+fourth = "{:.2f}".format(third)
+f"{first} {second} {first.upper()} {third} {fourth}"
+```
+
+_Dictionary_
+```python
+data = {'name': 'Hodor', 'email': 'holdthe@door.com'}
+txt = f'Name: {data["name"]}\nEmail: {data["email"]}'
+print(txt)
+```
+
+_Inline Math_
+```python
+hours = 21
+seconds = 32
+f"{hours} {seconds * 10} {seconds}"
+```
+
+_Inline Formatting_
+
+
+```python
+pi = 3.14159265359
+f"{format(pi, '.2f')}"
+```