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For a value you know is a Python string, use not value to check whether it is exactly empty, or not value.strip() to include strings made only of whitespace. Check None and NaN separately: they are not empty strings and need type-appropriate checks.
Check whether a string is exactly empty
Python treats the empty string "" as false in a Boolean context, so the simplest check is:
value = ""
if not value:
print("empty string")This matches a string with zero characters. A string containing spaces, tabs, or other characters is not exactly empty, so not value will not match it. Python’s truth-value rules and string type documentation describe this behavior.
Check whether a string is blank or whitespace-only
If whitespace-only text should count as blank, strip surrounding whitespace before testing:
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#1 Best Overall
- Read Before You Buy — No Video Output: These adapters support charging and USB 2.0 data transfer, but cannot transmit video signals. Except for standard USB webcams (which use USB data only), they are not compatible with HDMI/DisplayPort cables, video-capable USB-C hubs, or docking stations with video output.
- Convert USB-A Ports to USB-C: Designed to connect USB-C earphones, cables, flash drives, card readers, and other USB-C accessories to standard USB-A ports. Plug-and-play with no drivers or software required.
- Aluminum Alloy Housing: Built with a sturdy aluminum alloy shell that aids in heat dissipation and protects against daily wear and scratches. Designed to maintain a stable and secure connection.
- Compact & Travel-Friendly: The ultra-compact design allows the adapter to stay plugged into your device without blocking adjacent ports or adding bulk, reducing wear and tear on your original USB ports.
- 12-Month Warranty: Backed by a 12-month manufacturer warranty for peace of mind. Designed to meet strict quality control standards for reliable everyday performance.
value = " "
if not value.strip():
print("empty or whitespace-only string")str.strip() returns a string with leading and trailing whitespace removed. If the original contains only such whitespace, the result is "" and is false. If it contains non-whitespace text, the result remains nonempty. See Python’s documentation for str.strip().
Choose the check based on your definition of “empty”: not value means zero characters, while not value.strip() also treats whitespace-only strings as blank. Stripping is a check here; it does not modify value.
Rank #2
- 5-in-1 USB-C Hub: Experience comprehensive connectivity featuring a Power Delivery input, two USB-A 2.0 ports, a USB-A 3.0 port, and an HDMI port. (Note: The USB-C power delivery input port is only for connecting an external wall charger to power your laptop and cannot power peripheral devices.)
- 90W Pass-Through Charging: Achieve optimal charging with 90W pass-through power to your laptop, supported by a total input of 100W, with the hub reserving 10W for operational efficiency. (Note: Wall charger not included.)
- Quick Data Transfers: Accelerate your productivity with rapid data transfers using a high-speed 5Gbps USB 3.0 port and two 480Mbps USB 2.0 ports.
- 4K HDMI Display: Enhance your visual experience with a hub capable of delivering 4K resolution at 30Hz in both mirror and extend modes. Please note that this hub is compatible with MacBook (macOS 12 and newer), Windows 10 and 11, ChromeOS, and laptops equipped with DP Alt Mode and Power Delivery. Note: This device is not compatible with Linux.
- What You Get: Anker USB-C Hub (5-in-1, 4K HDMI), welcome guide, 18-month warranty, and our friendly customer service.
Handle values that may be None or not strings
None is a distinct singleton object, not an empty string. Test for it with is None. If a value may be None or a string, check its type before calling .strip():
if value is None:
print("missing value")
elif isinstance(value, str) and not value.strip():
print("empty or whitespace-only string")This keeps the cases separate and avoids calling a string method on a non-string value. Python documents None as a singleton.
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Rank #3
- Sleek 7-in-1 USB-C Hub: Features an HDMI port, two USB-A 3.0 ports, and a USB-C data port, each providing 5Gbps transfer speeds. It also includes a USB-C PD input port for charging up to 100W and dual SD and TF card slots, all in a compact design.
- Flawless 4K@60Hz Video with HDMI: Delivers exceptional clarity and smoothness with its 4K@60Hz HDMI port, making it ideal for high-definition presentations and entertainment. (Note: Only the HDMI port supports video projection; the USB-C port is for data transfer only.)
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- Fast and Reliable 85W Charging: Offers high-capacity, speedy charging for laptops up to 85W, so you spend less time tethered to an outlet and more time being productive.
- What You Get: Anker USB-C Hub (7-in-1), welcome guide, 18-month warranty, and our friendly customer service.
A bare truthiness check is not a general missing-value test. Values such as 0, False, and empty containers are also false in Boolean contexts. If those may be meaningful inputs, identify the type and intended meaning before applying a truthiness check.
Check for NaN and library missing values
NaN is a floating-point value, not a string. Equality is not a reliable way to detect it: NaN compares unequal to itself, so a comparison such as value == float("nan") does not work as a NaN check. Use the predicate appropriate to the value and library:
Rank #4
- Dual Converters, Infinite Potential：Includes 2× USB C male to USB A female adapters and 2× USB A male to USB C female adapters. Perfect for a wide range of uses—tablets with Bluetooth keyboards, expand USB ports on macbook, and more. Two different converters for all your daily needs
- Next-Level 10Gbps & 3A Charging: No more slow 480Mbps, this usb to usb c adapter has a transfer speed of up to 10Gbps, allowing you to do more transferring in less time. This usb adapter fits both USB A and USB C charger, supporting up to 3A fast charging
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- Broad Compatible: The usb c to usb adapter widely supports all USB C/ USB A devices like laptops, tablets, cellphones, car chargers, and phone chargers. Such as compatible with MacBook Pro/Air 2023/2022, Thunderbolt 4/3 Devices,Apple MagSafe Watch 9/8/7/SE/Ultra, iPad Pro 2022/2021, Samsung Galaxy S23/S20/S10, and iPhone 17/16/15 Pro. Plug and play
- Please Note: To reach 10Gbps speed, keep the cable under 3.3 ft. For USB A Male to USB C adapters, try flipping the USB C connector. USB C Male to USB A adapters support bidirectional 10Gbps transfer within 3.3 ft
- Compatible numeric scalar: use
math.isnan(value). - NumPy numeric value or array: use
np.isnan(value). - pandas-supported values: use
pd.isna(value).
import math
math.isnan(value)
import numpy as np
np.isnan(value)
import pandas as pd
pd.isna(value)NumPy documents the behavior of numpy.nan and provides numpy.isnan for detection. Use math.isnan for compatible numeric scalar inputs; do not pass arbitrary strings or objects without accounting for their types.
pandas isna recognizes supported missing values such as None, NaN, and NaT. With scalar input it returns a scalar Boolean; with array-like input, such as a Series or DataFrame, it returns array-like Boolean results. For an array or Series, use those results as a mask or combine them with an explicit reduction such as .any() or .all() when one overall Boolean is what you need. Do not use an array-like result directly as a single if condition.
Quick Recap
Best Value
- 5-in-1 Connectivity: Equipped with a 4K HDMI port, a 5 Gbps USB-C data port, two 5 Gbps USB-A ports, and a USB C 100W PD-IN port. Note: The USB C 100W PD-IN port supports only charging and does not support data transfer devices such as headphones or speakers.
- Powerful Pass-Through Charging: Supports up to 85W pass-through charging so you can power up your laptop while you use the hub. Note: Pass-through charging requires a charger (not included). Note: To achieve full power for iPad, we recommend using a 45W wall charger.
- Transfer Files in Seconds: Move files to and from your laptop at speeds of up to 5 Gbps via the USB-C and USB-A data ports. Note: The USB C 5Gbps Data port does not support video output.
- HD Display: Connect to the HDMI port to stream or mirror content to an external monitor in resolutions of up to 4K@30Hz. Note: The USB-C ports do not support video output.
- What You Get: Anker 332 USB-C Hub (5-in-1), welcome guide, our worry-free 18-month warranty, and friendly customer service.
Choose the check by input and intended meaning
| Input or question | Check | What it means |
|---|---|---|
| Known string; only zero characters count | not value |
Matches "", not whitespace-only strings. |
| Known string; whitespace-only also counts as blank | not value.strip() |
Matches empty strings and strings that become empty after stripping surrounding whitespace. |
Value may be None |
value is None |
Checks for the None singleton. |
| Compatible numeric scalar may be NaN | math.isnan(value) |
Checks for NaN in a numeric scalar. |
| NumPy value or array may contain NaN | np.isnan(value) |
Returns a Boolean result for a scalar or elementwise results for array-like input. |
| pandas-supported scalar or array-like data may be missing | pd.isna(value) |
Recognizes pandas missing values; result shape follows the input. |
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